The surgical tube drill is designed to help the player regulate leverage, allowing forearm rotation, simultaneously eliminating any foreward wrist snap.
Essentially, you want to get a piece of surgical tube with two loops at the ends. Note, that you will have to create the loops yourself. On one end, you will have a small loop that you will connect to the racket frame inbetween the 2 center main strings. You will then slip your arm through the second larger loop. The cord should be set at a length that will allow you to keep the double bend position (90 degree angle at both the wrist and the elbow).
By hitting forehands with this device, you will be making contact in the strongest leveraged position. You can also use the device on backhands, volleys and slices.