Boards
Did you have schoolbooks at your school that weren't covered in penis scribbles?
I vividly remember when we were at primary school and we had to spend a day at the secondary school to prepare us for it. We had a history lesson on the ancient Greeks and the textbook they handed round was quite a sight. Every man in it had about 3-4 pensises drawn on him. Often with speech bubbles saying things like "I'm gay".
I don't think I ever partook in this activity but it still makes me laugh.