Find out what car is theirs. Then get some razor blades and bluetack. Put the blades in the bluetack and stick to the underside of the handle.

They wont have any fingers left to turn the CD player on hahahaha1

Also, that's a good idea for security - i've done it before. You just gotta remember they're there. It's good though - you can see if anyones tried to nick your car - just judge the amount of blood and you can make a rough guess as to how many times the idiots tried before they gave up.