Two pieces of solid oak and a rubber band.
When the time comes - and eventually it will - put on a new rubber band. Just snatch the one from your lunch box.
You could also choose to toss the oak in the fire or in the woods. What ever you do, don't just throw it in the garbage. It's a naturally grown material. Please treat it with respect.
Comes with a simple hole to hang it on a pin on the wall.