When you say "fist to five check" students rate their understanding by holding up the appropriate number of fingers. The goal is for everyone to be in the green. Great way for students to self-assess their understanding and help you to gauge student understanding.
Nearly everyone all over the globe know that flashing the middle finger is meant as a huge insult to the recipient. However, many common hand gestures which are perfectly innocent to us are in fact quite dangerous in other parts of the world!