| at a workshop where I once worked we would have the operators coming in to report something wrong and have a bit of a chat , but while they were there thay could not help themselves and love to play with bits in the workshop. So on one of the benches close to where they would stop , we placed a blanking power outlet plate with just a little hole in it and a small screwdriver in the hole with just the handle showing ( a little excaliburs sword ). behind the plate was mounted a proximity switch which would be held switched bu the metal shaft of the screwdriver . when one of the fiddly boys came in and decided they would pull the screwdriver out , the prox switch would change state to allow power to a soleniod which would release 100psi to an airhorn and skidmarks would ensue. |