since someone started a topic in the offers forum with this topic, I rerouted it. I remember we had this friend who always looked in the bathroom cabinet every time they were at the house. so one day we took 100 marbles and rigged them in the cabinet with a piece of flat cardboard. we filled the cabinet and closed it while removing the cardboard. when he opened it, it made a loud crashing noise. after that he never went in the cabinet again