Speaking of pens, remember those buckram binders? Very fine threads. Most pens had a metal tip on top. We used to sit around in the cafeteria, during some of the bigger classes, running those pen tips back and forth and back and forth across the binder. Seven, eight, sometimes twelve of us at once.
You had to do this when the teacher had her back to us. Zwit, zwit, zwit, zwit, zwit. As soon as she turned around, we'd all stop. She probably figured we were abusing ourselves, or something, and always gave us this strange look.
Anyway, we kept rubbing the pen tips back and forth until the friction made them really hot.
Then you'd reach over and brand some poor schmuck on the back of his hand.
The poor schmuck, most of the time, was me.
Still got scars from that invention.