Okay, the knob doesn't actually move the billiard. I know that it does on one side, and that is sort of an accident and won't last very long. You have to move the billiard yourself when unscrewing the knob. When tightening the knob, it has the post to go up against so there's no need to move it there. But, undoing the knob requires you to move it with your hand.
Michael A. -- If your flaw in stringing is consistency, http://www.youtube.com/yulitle
MRT 07-08 -- your stringing will be consistently flawed.