When I meet with LJ's I give them a secret sign:
"If you are not sure, take your left hand, make it into a fist with the thumb on top of the fingers, then flick your thumb in the air."
"If you think I didn't see the sign then mouth the words "flip a --"
If they don't use flags, I give them a big set of signals to use:
1. If they don't know, Cover their eyes
2. If they didn't hear it, cover their ears,
3. If they heard the coach yell at them cover their mouth,
4. If they don't like my overrule, hold their nose, and I then run them from the gym....