I print one of these sheets, slip it in a sheet protector and hang it by the classroom door. The kids put a clothespin on their name when they leave to go to the restroom, retrieve the lunch crate etc. I can quickly see who is out of the room and also grab it on my way out for a fire drill. This makes it very easy to see how many kids I should have and who I may be missing. It is also quick and easy to update when students move in or out of my class.