Just made lemon bars. When do I cut them...while hot or cooled?

Absolutely! When they are completely cooled, cut away!

Definitely wait until cooled - I would even put them in the fridge for about an hour or so to make sure they are completely set before cutting.

not just cooled but cooled and CHILLED til COLD> otherwise, they can tear when you try to cut them.

Yes! Wait until they're cooled.

I would wait to cut into bars until its completely cooled.