Small punch card bathroom passes that can be used in any classroom. They come 8 to a sheet and are to be printed double sided so that the pass is on the front with the directions on the back. I like to print them on colorful paper and then laminate them so that they are more durable throughout the semester or year.
There are three stars to hole punch, one each time a student uses the pass. I gave my students a few points of extra credit for leftover stars at the end of the semester.