The performer shows a padlock and passes out four keys to four spectators. Each tries his or her key in the lock. The keys turn but do not open the lock. The spectators are each given a small coin envelope and instructed to seal their key inside.
A fifth key is brought out. The lock can be opened only with this one key. It is also sealed into an envelope. The envelopes are held and shuffled by a spectator. One of the spectators locks the lock.
The envelopes are mixed and the performer selects an envelope.
The key is removed from the envelope and the performer now opens the lock with the correct key.