Conceived and photographed at red lights on the way to work. The knob was missing on my car radio when I inherited this car, and it is really annoying. When I scrapped an old CD player, its knob popped off while I was carting it around in the car. I got this idea when the knob rolled under my feet.
You will need:
A radio missing a knob
A knob from another useless device
It is best if the knob has a slot in it
Step 1: Insert Penny into knob
If your knob does not have a slot in its post, you could possibly create one, or maybe use an epoxy.