[just another ref]

Originally Posted by Snaqwells

I disagree with it. Usually, it seems this contact is because the rebounder is sticking his elbows where he has no right to have them.

I may have overstated the point. When it's a rebounder, I agree with you. Let's try it this way. If a player is standing vertically as he should, he'll be okay, of course. But when a player assumes an improper posture, defensively speaking he sometimes leads with his chin, and may easily create the contact with it.