I use this sign-out log on a clipboard with my middle school students, and it remains hanging near the classroom door throughout the year. The rules are explained to students at the beginning of the year (or right before its implementation), but the rules are also posted at the bottom of each page as a reminder. I use a generic bathroom pass in conjunction with the log - only one student out at a time.
There are spaces for the date, student's name, time out, and time back in. It's a word file that can be modified with your own room number, or in any other way you see fit!