Who is responsible for placing the checkout divider between groceries?

[RASQ]

I always place the divider behind my groceries when I'm done putting them on the conveyor. I have notice some folks don't do this and they'll get the dirty look.

Is there some rule that the person with room behind their groceries is responsible for placing the checkout divider on the conveyor-belt so the other person can then place their groceries on the conveyor?