The magician borrows a solid ring from a spectator showing how it is impossible to lock it over the shaft of a large metal key. He hands both the key and the ring to many spectators asking them to try lock them up
but only the magician, after bringing his hands behind his back, will succeed in this challenge and will show the ring locked over the shaft of the key.
Pocket-size, take it anywhere you go.
You can remove or replace the ring whenever you wish to.
Spectators wont be able to find out the cleaver secret, thanks to a special precision metal mechanism.