Who says you can't win 'em all??
What an amazing and USEFUL effect to add to your show! There are so many ways to present this trick that you can perform it a different way every time!
The concept is simple. You decide whether a key will open the padlock or not.
And how would you present this trick? Well, you could show the three keys, and show that only one will open the lock. You mix the keys up, then let your spectator FREELY CHOOSE any one of the three keys. You can even let him change his mind and select a different one. Then let another spectator choose a key from one of the two remaining. No matter which keys are chosen, YOUR KEY (the key that your spectators did not choose) is the only key that will open the lock.
Or you can reverse the effect. Show that only one key opens the lock. Let your spectator mix them up, and hold them in their hand. Without looking, you hold your hand over the keys, mentally picking up "energy", and you select one of the keys. Of course, the key will open the lock.
There are countless ways you can use this effect. ALL the keys fit into the lock, and ALL the keys can open the lock. You just choose when! Use it for a timed escape, use it in a mentalism routine, even use it in a comedy routine. If you are performing at an event in honor of a specific guest (a retirement or birthday party), you can let the guest choose the correct key. So many possibilities! This is one trick that you will get a LOT of use out of!