Tie either a can of paint to the door knob and to something hang-able on the ceiling. Make sure the string is long enough to reach the ceiling. 3 helpful tips- the paint canshould be un-noticable. Best to do on boys- use pink paint!! Set up for this prank during free time or when you are in the middle of a game- make an excuse that you have to go to the bathroom and set up then. ENJOY!!