Another question....about grading participation/attendance

So a reader Crystal left a question, asking how I grade participation/attendance, of which I allot 20% of the final grade.

My system is quite simple, compared to many of my colleagues.

I have an ink stamp, and I stamp the backs of their textbooks. If the student is sitting in their desk, the minute class starts with their pen, book, and name-tag, they get one stamp. The stamp=1%. In addition, almost everything we do in class has a winner of some sort and this person gets a stamp. If someone volunteers to help me by doing a demo, they'll get a stamp.

That's it.