Bending the topic a little, but not much.
We can from, time to time, get straight-lined, because of a quick pass (
or a quick nap), and we just cannot see the line.
It is at those hopefully few times, that we hope our partner did have a look.
The mechanic is to not signal, but look at our partner. If he gives us three we're good, if not we pass.
During the two minute, dead ball game when we get together to pump ourselves up for the final seconds of a close game, I often mention "Let's make sure we help each other on the Threes."
mick