I remember once a guy had 2 plates on the Hack. He asked a pretty strong female bb there for a spot on his set. She agreed to watch him, even though she knew there was hardly any weight on the thing. What she didn’t know was that the guy was on his last exercise of a super or giant set and was fatiguing pretty badly.
Anyway, the guy un-racked it, did a few seemingly easy reps, then damn near collapsed suddenly. Fortunately, she was there to help, but it caught her completely off guard, and I know she later admitted to not showing the proper attention the set deserved. The guy pulled something – it was minor – but this incident could have been better avoided with better communication between the two of them.
Doesn’t even have to be at all detailed.
Look:
"Hey, could you watch me on this?"
"Sure, how many are you going for?"
"Not sure, but stay close."
Simple.