A borrowed ring is placed on a brass padlock with a combination and the 4 digits on the dial are mixed up. The magician can ask the audience for a 4-digit combination, but the padlock won't open. The magician then asks the owner of the ring to tell him his wedding date and, amazingly, this is the only combination that opens the padlock. The magician could never have known. Everything is mechanical, with no magnets, wires, timers, switches or electronic parts. It's the spectator who sets the chosen numbers and places them on the padlock.