Here is a template of exit tickets that ask the following two questions:
List 1 thing that you have learned.
List 1 thing that you still do not understand.
It's a great way to measure what students understand and what they need extra help with. I use these tickets in math class on Thursdays and go over their questions at the beginning of class on Fridays. Great way for students to express their concerns on topics that they don't quite understand without feeling embarrassed in front of the class.