Single handed backhand - technical questions

[tex123]

if you grab a racket and shadow the windshield wiping motion -

wiping counter clockwise is ISR; wiping clockwise is ESR.

Hey Geca - Brady's technique is very different to Henin's. I can see ISR in Henin backhand very clearly. But Brady uses a straight arm takeback and drives the butt cap towards the ball. I don't see any ISR here.

What does ISR contribute to the stroke? Can I not just start from there ( Henin racket dropped position ) and wipe the ball?

 

[Raul_SJ]

All of those pics, Raul_SJ. If I hold the racket tightly with _all_ knuckles on bevel 1, it c ocks the wrist in Pic 1. From there onwards, he maintains that angle throughout the stroke. It is only possible when the racket is gripped tightly. In a forehand, I have loose grip and wrist is not c ocked at all. We probably tighten it at the point of impact. It is very easy for anyone to pull theracket out of your forehand grip. But in a 1hbh backhand grip - no.

Brady's technique is very different from Henin (bent arm takeback). I don't see any ISR in Brady's backhand. But in Henin backhand, ISR is very clearly seen. That's a question for Geca.

I've always tried to keep the same loose grip on forehands and backhands and not aware of backhands requiring tighter grips. Maybe others can comment on that...

As far as ISR, I believe ISR occurs on every high level backhand drive. It creates the "inverted C" path, racquet tip pointed upward to the sky and facilitates greater racquet head speed. Here is the Brady ISR.

I am not sure of what the significance of a bent arm takeback like Henin is. It might be just personal preference. Most of the instruction I've seen advocates straight arm takeback.

 

[Chas Tennis]

Here are some frames from the Haas backhand video in post #18. Keep in mind, the height of the incoming ball may affect the ISR phase.

Frame #1. His turn back showing his upper body turn with his back somewhat facing opponent, non-hitting elbow height and racket orientation(more upright less open than Gasquet).

Frame #2. Haas is swinging forward, presumably has done ISR & pronation(?), and is leading with the butt of the racket. My opinion - this is not a heavy paced backhand because he has not uncoiled his upper body forcefully enough.

Frame #3. Between Frame #2 & 3 he has done ESR & Supination(?). You can see ESR by the wrist-palm-racket orientation. It appears that he is using ESR & Supination(?) for racket head speed.

Frame #4. He continues with ESR & Supination(?) to impact.

This ESR before impact may be the action that geca is emphasizing. ?

I've looked at a few of the highest level one hand backhands to see what they are doing. Gasquet, Wawrinka and Henin stand out but there are several others with superior backhands. There are commonalities because of the biomechanics but I don't know the details of racket angles, etc.. I don't know the other variations of strong 1hbhs that are out there.

 

[geca]

Hey Geca - Brady's technique is very different to Henin's. I can see ISR in Henin backhand very clearly. But Brady uses a straight arm takeback and drives the butt cap towards the ball. I don't see any ISR here.

What does ISR contribute to the stroke? Can I not just start from there ( Henin racket dropped position ) and wipe the ball?

this is quite a can of worms lol.

personally i don't care about straight/bent arm. if you just shadow a windshield wiping (WW) motion, does it really matter if the arm is bent or straight? fundamentally there is no difference, you have some upper arm bone rotation (shoulder rotation), and a little bit of forearm bone rotation.. except a bent arm gives a bigger range of motion.

and what does ISR contribute? in every hitting sport there is this thing called 'loading' lol... if you let the racket fall into the power position, your shoulder and forearm is then loaded with power... by the way this is also why I personally use a bend arm because the weight of the forearm allows the fall into a more loaded power position.... also for practical matters, the ball might take a funny bounce or blown by gust, the bend arm allows you to deal with these situations more easily.

anyway, back to loading.. if you let the trailing edge to lead the fall from the upright position into the power position, you are guaranteed to have a correct ISR.... the most common mistake is to let the non-hitting side of the strings lead the fall, then you have an open face..

this is also associated with your 'intent' during the shot. the common mistake is to try to 'hit' the ball with the strings, then you have the non-hitting side of the strings leading the fall, and the hitting side strings leading the forward swing... this will result in opening/shutting of the face, and the shot is ruined.

the correct intent is to WW. let the trailing edge lead the fall, and accelerate the leading edge to the ball (isn't that what you do if you try to WW forcefully? lol).... as if you try to cut the ball with the leading edge.... this guarantees a constant loft (a slightly closed face) coming out of the power position, thru impact, into the racket release.

1 more point about falling (ISR) into the power position.... when you progress, you will need to deal with higher balls (I can rip a ball 2 feet above my head, makes the strike zone seamless with the backhand overhead smash lol).... it's virtually impossible to 'just put the racket in the power position' without an ISR into the power position.

by the way all this discussion seems to support my initial point that the key element hasn't been discussed enough... also a couple of fellow posters supported the view that the hand motion and racket path is THE key to this shot (or any other tennis shot for that matter)

 

[Chas Tennis]

......................

personally i don't care about straight/bent arm. if you just shadow a windshield wiping (WW) motion, does it really matter if the arm is bent or straight? fundamentally there is no difference, you have some upper arm bone rotation (shoulder rotation), and a little bit of forearm bone rotation.. except a bent arm gives a bigger range of motion.

and what does ISR contribute? in every hitting sport there is this thing called 'loading' lol... if you let the racket fall into the power position, your shoulder and forearm is then loaded with power... by the way this is also why I personally use a bend arm because the weight of the forearm allows the fall into a more loaded power position.... also for practical matters, the ball might take a funny bounce or blown by gust, the bend arm allows you to deal with these situations more easily.

anyway, back to loading.. if you let the trailing edge to lead the fall from the upright position into the power position, you are guaranteed to have a correct ISR.... the most common mistake is to let the non-hitting side of the strings lead the fall, then you have an open face..

this is also associated with your 'intent' during the shot. the common mistake is to try to 'hit' the ball with the strings, then you have the non-hitting side of the strings leading the fall, and the hitting side strings leading the forward swing... this will result in opening/shutting of the face, and the shot is ruined.

the correct intent is to WW. let the trailing edge lead the fall, and accelerate the leading edge to the ball (isn't that what you do if you try to WW forcefully? lol).... as if you try to cut the ball with the leading edge.... this guarantees a constant loft (a slightly closed face) coming out of the power position, thru impact, into the racket release.

1 more point about falling (ISR) into the power position.... when you progress, you will need to deal with higher balls (I can rip a ball 2 feet above my head, makes the strike zone seamless with the backhand overhead smash lol).... it's virtually impossible to 'just put the racket in the power position' without an ISR into the power position.

by the way all this discussion seems to support my initial point that the key element hasn't been discussed enough... also a couple of fellow posters supported the view that the hand motion and racket path is THE key to this shot (or any other tennis shot for that matter)

You have a lot of very interesting points but I am always uncertain as to what part of the backhand motion you are referring to. I don't know what the "power position" is for the 1h backhand. I'm lost with 'leading edge' and 'trailing edge' when the racket butt faces the ball.

Posting a few frames to illustrate the exact times and positions that you mean goes a long way toward clarity. I can list the process for posting frames from videos.

 

[geca]

@Chas - I wouldn't worry too much about some differences among the pros... they are all hitting the same shot lol.... they might look different because their body structures are different.

regarding the ESR and supination during the forward swing - the forearm is actually passive.... so the acceleration starts with the shoulder rotation, the the supination just happens.

the entire arm is passive.. you ISR into the power position by allowing the forearm and the racket to fall (loading), this happens while you coil the upper body....

then by uncoiling the upper body the ESR and supination just happens.

 

[geca]

You have a lot of very interesting points but I am always uncertain as to what part of the backhand motion you are referring to. I don't know what the "power position" for the 1h backhand is. Posting a few frames to illustrate the exact times and positions that you mean goes a long way toward clarity.

I can list the process for posting frames from videos.

power position refers to the extreme of the back swing, (also the very start of the forward swing.)

and feel free to drop me a note.. some of this stuff is easier verbally.

 

[geca]

in the haas video the power position is at 8.5 seconds.

 

[geca]

Hey Geca - Brady's technique is very different to Henin's. I can see ISR in Henin backhand very clearly. But Brady uses a straight arm takeback and drives the butt cap towards the ball. I don't see any ISR here.

What does ISR contribute to the stroke? Can I not just start from there ( Henin racket dropped position ) and wipe the ball?

please see my recent post on the purpose of the ISR

 

[Chas Tennis]

please see my recent post on the purpose of the ISR

What post is that?

 

[Raul_SJ]

A common error is backhand floating long or going short due to non-vertical face angle at contact.

This Tom Avery video says that if you take care that the face is closed at the low point of the backswing, as in the pic below, it will ensure the face will be vertical at contact. (As long as you swing from the shoulder, without wrist/forearm movements).

 

[geca]

I don't like Avery's teaching.

yeah racket face is closed in the power position... but how much closed? how do you get there? the way he gets to the power position is stiff and not optimal - no modern pros do that.

ISR let the racket falling into the power position is how it's done in today's game.

also notice the difference in the contact height... the old school way he shows likes the contact at waist or lower... it's ok if everybody uses wooden rackets.

with ISR/ESR the optimal contact is at chest high - that's how the pros do it.

 

[Raul_SJ]

I don't like Avery's teaching.

yeah racket face is closed in the power position... but how much closed? how do you get there? the way he gets to the power position is stiff and not optimal - no modern pros do that.

ISR let the racket falling into the power position is how it's done in today's game.

also notice the difference in the contact height... the old school way he shows likes the contact at waist or lower... it's ok if everybody uses wooden rackets.

with ISR/ESR the optimal contact is at chest high - that's how the pros do it.

I will have to check out the "power position" Haas video and re-read your posts as I'm not clear on some of the terminology, e.g., "the most common mistake is to let the non-hitting side of the strings lead the fall, then you have an open face.."

The Avery video makes sense to me as it addresses the common problem rec players encounter: how to achieve a vertical face at contact...

 

[geca]

edited.

 

[geca]

I will have to check out the "power position" Haas video and re-read your posts as I'm not clear on some of the terminology, e.g., "the most common mistake is to let the non-hitting side of the strings lead the fall, then you have an open face.."

The Avery video makes sense to me as it addresses the common problem rec players encounter: how to achieve a vertical face at contact...

the bottom line is, as I have written, the modern 1hbh does not try to 'hit' the ball with the strings. the intent is to roll the ball with a WW motion...

so you WW counter clockwise (ISR, racket falling withe trailing edge leading the fall) while turning the shoulder back to get to the power position.

then you unwind the shoulder while accelerating the leading edge (not the strings) to the ball. ESR happens automatically.

 

[geca]

just go out there hit a few balls and you will instantly feel the improvement... I told a couple of guys to accelerate the leading edge and their shots got better immediately.

 

[geca]

also - I think it's necessary to point out bad teachings. otherwise you will be in for a load of frustration.

Avery's are not that good... but these below are even worse -

stuff like this... shots are useless on anything above waist height because without the ESR motion the contact is too low.... it's funny that both put 'Roger Federer' in the titles, when they basically have no clue about how Roger actually hits it lol.

compare to the ATP pros where the average contact is around chest high.

this is a good one... you see the similarity to the ATP style.

 

[Chas Tennis]

in the haas video the power position is at 8.5 seconds.

Frame #1. I counted 15 frames past 8.0 sec on my Quicktime display. (30 frames advance moves the time to 9.0 seconds.) Probably this frame is nearest 8.5 seconds.

Frame #2. The next frame of the original video, the racket is lower. Is this the 'power position'? The only use that I'm familiar with for the term 'power position' is as an undefined term for the serve. I can't distinguish 'Power Position' from the Trophy Position.

Frame #3. The next frame shows forward racket motion. An interesting interpretation based on the position of the faint bone shadow at the elbow is that Hass has done some ESR from Frame #2 to #3 with the upper arm rotating around its axis. However, the racket seems in the same orientation in Frames 2 &3 even though there was some ESR. Maybe his forearm had lagged and pronated some and stretched his supination muscles. That can't be seen too well based on just the elbow shadow but because of the inertial of the racket and forearm that is what should happen with fast ESR especially with a relaxed arm.

If you want to post a picture to illustrate "power position" right click on the picture. Select "Copy Image Location". You can then paste the Image Location into the box that appears after clicking on the image icon (icon looks like two mountains above the Reply or Edit box.)

(PS - I find that I learn a lot when I try to post pictures that don't exactly fit my my mental picture and even show new stuff like the frame above.)

 

[geca]

The Avery video makes sense to me as it addresses the common problem rec players encounter: how to achieve a vertical face at contact...

actually the more I thought about it, Avery's teaching is wrong.

if you WW, the face should stay the same and never change - I used the term 'constant loft' in this thread.

in reality the face is NOT vertical at impact... it's a few degrees closed.. similar to a modern FH.

let's say it's 5d closed at impact, then it should be 5d at the power position, 5d at impact, 5d in the follow thru.

the loft change from 'closed' to 'vertical', as Avery teaches it, is exactly the demise of the old school shot... because after the 'vertical position' it keeps opening up, which renders the shot useless on any balls above the waist.... which is also in the 2 'bad' videos above these teachers can only drop a couple and hit at knee high... put them in a real battle situation those shots will fall apart.

 

[geca]

power position at 0:16, basically when you start the pull forward.

also notice the 'constant loft' from :48 - :50 .... power position to impact to follow thru... 5d closed all the way.... there are few more shots after :50 from the same angle, you can see the constant loft on every shot.

 

[Chas Tennis]

power position at 0:16, basically when you start the pull forward.

also notice the 'constant loft' from :48 - :50 .... power position to impact to follow thru... 5d closed all the way.... there are few more shots after :50 from the same angle, you can see the constant loft on every shot.

That video illustrates your point very well.

 

[tex123]

compare to the ATP pros where the average contact is around chest high.

this is a good one... you see the similarity to the ATP style.

That video is AWESOME. I understand a bit better. And he shows the power position as well (he calls it leverage)

 

[tex123]

I've always tried to keep the same loose grip on forehands and backhands and not aware of backhands requiring tighter grips. Maybe others can comment on that...

As far as ISR, I believe ISR occurs on every high level backhand drive. It creates the "inverted C" path, racquet tip pointed upward to the sky and facilitates greater racquet head speed. Here is the Brady ISR.

I am not sure of what the significance of a bent arm takeback like Henin is. It might be just personal preference. Most of the instruction I've seen advocates straight arm takeback.

Cheers for posting that, Raul_SJ. Hard to see when there are so many moving parts. I agree there is ISR looking at that.

Regarding the take back - amongst the players with superior backhands, only Nico Almagro has a straight arm takeback. Waw, Fed, Gasq, Henin .. all have bent arm. Maybe it is just personal preference. I don't know enough about it.

I think you will find a "solid feel" when you hold it tight (with all knuckles on bevel 1) unlike a forehand grip. I certainly do.

 

[Chas Tennis]

.............................

As far as ISR, I believe ISR occurs on every high level backhand drive. It creates the "inverted C" path, racquet tip pointed upward to the sky and facilitates greater racquet head speed. Here is the Brady ISR.

I am not sure of what the significance of a bent arm takeback like Henin is. It might be just personal preference. Most of the instruction I've seen advocates straight arm takeback.

When do you mean that the elbow is straight? A quick look at a few of the best one hand backhands all shows the elbow flexed. Included are Henin, Gasquet, Wawrinka, Haas all pictured in this thread.
https://www.google.com/search?q=one...4yihJvLAhWJyj4KHbGRB1MQsAQIHg&biw=895&bih=573

Do you have the video used for that Brady gif?

 

[Chas Tennis]

..........................................................................
compare to the ATP pros where the average contact is around chest high.

this is a good one... you see the similarity to the ATP style.

Here are a few frames on the issues that we have been discussing. This is a very good camera view to show how the racket comes out away from the body.

Frame #1. The take back similar to Gasquet and others with racket face open to sky. Henin's racket in the video above is different, not so open.

Frame #2. The racket is down and presumably ISR has occurred. He has moved forward. Nose close to fence pole.

Frame #3. His head is in the same place as Frame #2. The racket has moved butt first toward the ball. In my opinion, his shoulder girdle would have rotated more for a very heavy paced drive. ?

Frame #4. Near impact. The ESR is not clear to me between Frames #3 to 4. They say that Federer looks through the racket strings from the back at ball impact on some strokes. It looks as if the instructor may be looking through the racket strings from the back. ?

I'd like to study other backhands from this camera angle.

 

[geca]

@Chas I think you got it.... yes during the take back the racket face looks open to the sky, but the WW action does not change.... the ISR is happening while Kevin takes it back and drops it down.

biomechanically speaking, because there is a big space above the left shoulder, it is the most comfortable to turn back and have the racket the hitting hand in that space to start... then you drop it down into the loaded power position.

in the above sequence Kevin hit a ball just below his chest.... I'd personally not having the hands so high in the take back for such a ball.... but it's just personal preference... If I need to hit a shoulder high ball, then a high take back is definitely ideal.

 

[geca]

by the way - look at this weekend.... Wawa won Dubai, Thiem won Mex, and the 2 finalists in Brazil are both 1h....

3-tour sweep for the 1hbh....this shot is live and well on the tour!

 

[Shroud]

I've always tried to keep the same loose grip on forehands and backhands and not aware of backhands requiring tighter grips. Maybe others can comment on that...

As far as ISR, I believe ISR occurs on every high level backhand drive. It creates the "inverted C" path, racquet tip pointed upward to the sky and facilitates greater racquet head speed. Here is the Brady ISR.

I am not sure of what the significance of a bent arm takeback like Henin is. It might be just personal preference. Most of the instruction I've seen advocates straight arm takeback.

I for one dont grip tight, though i used to. Its mich better for the elbow and for fluidity

If you have a sw grip the ww makes even more sense IMHO as its natural, like waving.

 

[Shroud]

by the way - look at this weekend.... Wawa won Dubai, Thiem won Mex, and the 2 finalists in Brazil are both 1h....

3-tour sweep for the 1hbh....this shot is live and well on the tour!

Yeah!!! Thats awesome. Love the 1 hander!!

I have said that the 1 hander is in an evolutionary phase and this thread IMHO shows that not every one gets the evolution yet...and explains why coaches freak at my bh initially but when i actually hit it they kind of chill, especially when they see the grip i use

 

[geca]

I for one dont grip tight, though i used to. Its mich better for the elbow and for fluidity

If you have a sw grip the ww makes even more sense IMHO as its natural, like waving.

agreed on the grip - should be loose to allow the ISR loading and the ESR unloading.

 

[Shroud]

I'd like to study other backhands from this camera angle.

Hey Chas, not saying its a good bh but uou can use this vid if you want as its the same angle. Hopefully there are some common elements

 

[Limpinhitter]

Limpin, an old name I see. Welcome back

Thank you!

 

[Yaz]

by the way - look at this weekend.... Wawa won Dubai, Thiem won Mex, and the 2 finalists in Brazil are both 1h....

3-tour sweep for the 1hbh....this shot is live and well on the tour!

Don't forget Suarez-Navarro winning Qatar

 

[geca]

Don't forget Suarez-Navarro winning Qatar

oh.. yeah!

 

[Chas Tennis]

Hey Chas, not saying its a good bh but uou can use this vid if you want as its the same angle. Hopefully there are some common elements

That is a nice motion. You use your upper body turn.

I had just noticed the ISR/ESR motion, that geca is talking about, in November 2015 so I have not looked much at the top backhands. I don't understand the ISR/ESR motion very well and especially the forces. Backhand drives are hit with a lot of variation in pace and topspin so the techniques used by each player will vary. I don't know the variety being used or have checkpoints as I do for the serve. I'll study what the top players do when they want to hit a winner.

I would say that your backhand does not use the ISR/ESR as much as Henin and probably the others.

Frame #1. The racket appears to have a similar open orientation as Gasquet and some others. Probably your hitting arm and especially the other elbow are more to the front?

Frame #2. Henin for comparison. Henin's racket is not as open as Gasquet's. She has a lot of upper body turn and some upper body to hip 'separation' (the upper body is turned back farther than the hips.)

Frame #3. The thing that is important for the ISR/ESR issue is that you more bring your racket down where Henin rotates her racket down. Her motion has more ISR possibly caused by the off hand moving the racket head. Compare videos, yours to Henin's. Also, compare your forearm to racket angle to Henin's and others with similar camera angles. The camera angle is not so good for seeing your forearm to racket angle. Her's looks 90d and yours much straighter.

Frame #4. Henin for comparison. Her forearm to racket is about 90d. Find others.

Frame #5. Near impact. ESR here would add to topspin.

Frame #6. After impact.

Frames #3, 5 and 6. Look at video and try to see ESR and the general racket path. I think you are swinging forward with less ESR than most strong drives of the top backhands. But I have not looked at enough heavy paced backhands to know.

Henin's backhand starts at about 56 seconds with racket drop at 1:07. The way the racket rotates down is a pretty distinct and simple motion, don't you think?

 

[tennis_balla]

So much complexity for such a simple shot.

 

[tex123]

That is a nice motion. You use your upper body turn.


Frame #3. The thing that is important for the ISR/ESR issue is that you more bring your racket down where Henin rotates her racket down. Her motion has more ISR possibly caused by the off hand moving the racket head. Compare videos, yours to Henin's, to compare. Also, compare your forearm to racket angle to Henin's and others with similar camera angles. The camera angle is not so good for seeing your forearm to racket angle. Her's looks 90d and your much straighter. ?

Frame #4. Henin for comparison. Her forearm to racket is about 90d. Find others.

I think that's a result of loose grip pressure. Wrist flexion may be causing it to point to the back fence instead of side fence like Henin. IMHO It is much easier to maintain forearm to racket angle with a tighter grip.

 

[tex123]

So much complexity for such a simple shot.

No pain, no gain

 

[tennis_balla]

No pain, no gain

To each his own.

 

[tex123]

Jeff talks about grip pressure on 1hbh with a pro.

There's no way one could finish with a flourish like he does (and Kevin and Brady) with a loose grip.

 

[geca]

Shroud's bh is sound... although with all due respect you can't really compare a top pro to a middle aged guy in long pants and a hoodie lol.

@Chas I think at this point it's over analyzing.... time to roll some balls.

Balla is probably being sarcastic.... but once you roll some balls and feel the hand action, it is really that simple.

 

[Chas Tennis]

geca, how did you learn about the ISR & ESR aspect of the one hand backhand?

 

[geca]

geca, how did you learn about the ISR & ESR aspect of the one hand backhand?

similar to a few fellow posters, I believe the key to any shot is the hand action that guarantees a constant loft. ... just experimented and figured out what action has the constant loft and that was it.

fundamentally it's no different from a WW forehand. you are just wiping in the opposite direction.

 

[tennis_balla]

I'm not being sarcastic at all. You guys are making something that's very simple overly complex with unnecessary terms and analysis.

 

[geca]

I'm not being sarcastic at all. You guys are making something that's very simple overly complex with unnecessary terms and analysis.

how do you teach it... am all ears.

not complex at all - wax on wax off.... people will have questions, then detailed answers are needed.

actually when i tell others on the court, it did just take a couple of minutes.... but on such forum it's a lot of typing.

 

[Limpinhitter]

When do you mean that the elbow is straight? A quick look at a few of the best one hand backhands all shows the elbow flexed. Included are Henin, Gasquet, Wawrinka, Haas all pictured in this thread.
https://www.google.com/search?q=one...4yihJvLAhWJyj4KHbGRB1MQsAQIHg&biw=895&bih=573

Do you have the video used for that Brady gif?

In my view, the elbow should be straight before the start of the forward swing. Takeback isn't critical.

 

[geca]

the arm will straighten some in the forward swing due to the centrifugal force.... but there is no need to use the arm muscle to straighten and lock the elbow.... the motion should be relaxed and fluid.

 

[Cheetah]

The arm is not straightened due to to centrifugal force. Also loose grip is not related to ease of Isr / esr especially on the 1hbh.

 

[Limpinhitter]

the arm will straighten some in the forward swing due to the centrifugal force.... but there is no need to use the arm muscle to straighten and lock the elbow.... the motion should be relaxed and fluid.

As long as the arm is straight well before contact, I think it should be fine.

 

[Chas Tennis]

similar to a few fellow posters, I believe the key to any shot is the hand action that guarantees a constant loft. ... just experimented and figured out what action has the constant loft and that was it.

fundamentally it's no different from a WW forehand. you are just wiping in the opposite direction.

Did mini tennis play a part? If you hit with low pace does the ESR itself propel the ball adequately?

When Henin described ESR in a Tennis Channel show I had the impression that she was saying and demonstrating that the function of ESR was topspin. The Haas video looked as if ESR could be for racket head speed as well as TS. ? Did you say ESR was just freewheeling from earlier motion? Interesting questions.

The term 'loft' is new to me even after reading the forum for five years. Do you mean that the racket is open to a constant angle, or just has a constant angle, or that the ball is lofted - rises after it is hit? Isn't it slightly closed at impact and the ball goes up? I like the open-closed terminology.