The purpose of this drill is to teach the quarterback to quickly and automatically, "mold" the ball into his hands, and into a proper passing position without having to look at it. When an inexperienced quarterback gets ready to throw, he usually looks at the ball and carefully places his hands so that the fingers are in just the right position across the laces. The ball exchange between the center and quarterback is planned so that the ball should always hit underneath the finger tips of the passing hand. However, in the case the ball isn't received properly from the center, or on plays where the quarterback is to throw a delayed pass after taking a toss or hand back from one of the other backfield men, it should still not be necessary or the quarterback to look at the ball in order to grip it properly for passing.
On this particular drill you should keep the ball moving as fast as possible. The instant the ball hits the hands you should "mold" it so that you can grip the laces while at the same time lifting the ball up to the proper passing position outside of your right ear, then making the return pass to his partner with as little delay as possible, and without having ever looked at the ball.