Start with the bounce, not the wall
The fastest way to sort out a wall dispute is to agree on the bounce sequence before you talk about glass or fence. That keeps legal rebounds separate from points that were already dead.
In real matches, the confusion usually starts when a fast rally reaches the side glass or back fence and everyone reacts before anyone calls what happened first.
- Call the floor bounce first.
- Call the next surface the ball touched.
- Decide whether the return was still legal after that sequence.