In answer to ChrisDavid who asked "Am I understanding that the Key-R-Rect padlock is constructed in such a way that no switch of keys is made during routine. Only the 6 (or 7) keys are used and the locks ability to open is under your control?"
You do have to switch the master key with a dud key if you are going to allow others to try the lock after the lock is opened by the "key" during the routine. You switch the master key (that is the actual key that can open the lock whether it is locked in position one or two) right after the lock is first opened (and when no one would suspect a switch of the key) and once the lock is opened the second time with whatever key is selected, it is a simple matter to "double lock" the lock once more so that no other key (except the master which is now secured in your pocket or elsewhere) will open the lock, thus allowing you to have it examined and tested with the other keys.
Also, Stan KRAMIEN posted "The key r ect version that I have, I believe was from Supreme, years ago,,it came with a nice plastic fold over that you can put a hundred dollar bill in, and of course lock throuth the holes and the bill,,,If you are lacking in guts, use a dollar bill..I have done it hundreds of times, and use it in my current (yes, I am still working) show,,now stop talking about it, and buy one from Joe,,he has two versions,,,"
Repro Magic sells a gravity lock set-up with a plastic holder for the bill which incidentally when held with the lock hanging allows you to position the lock without touching it for the spectator to try and imperceptibly you can have it in position to open or not depending on which you desire.
A nice thing to do with this routine is not for you the performer to wind up with the winning key to open the holder but instead for you the performer to correctly guide your participant in finding the key that opens the lock and by doing so they win the cash inside the holder. Rather the the participant walking away a loser, they walk away a winner and since you the performer have successfuly guided the participant into winning a large cash prize (good rule of thumb is to have 10% of your fee as the prize) you look even better.
Also think of the added publicity when audiences know that one of them could win "insert the amount of cash or prize). creates a lot of excitement. And, it can be used in a trade show or shopping mall show using gift certificates (a nice plug for your show sponser) if you wish with the added bonus that your sponser covers that cost and it still makes you look great in the eyes of everyone.
Paul Alberstat http://www.mindguy.com