Now, I never stopped to think about the amount of dexterity it actually requires to tie a knot. In fact, it seems that this simple task is completely impossible to perform using the small mechanical graspers with which most of the rest of the surgery is performed. The accepted solution, then is to pull the 2 limbs of the suture outside the body, to tie the knots by hand, and then, using the knot pusher, to push the knot back into the body and to tighten it at the appropriate site. That little notch you see in the tip of the knot pusher is so that you don’t loose track of the knot on the way in. Pure genius.