[mplagrow]

Originally Posted by rainmaker

I make the motion, sometimes even bending at the waist to reach really low, and really high, and say, "Glass wall". If there are the blank stares, I say, "Understand?" I don't see this as instructing, I see it as self-defense.

Consider this preventative officiating, along with making sure the defender gives some space in a small gym and the thrower's back is to the wall or bleachers.