Have a volunteer put one hand on top of the other
Magician then pushes top hand off bottom hand using only one finger. Now have volunteer do the same to the magician. It will be impossible.
(Place pointer on photo to see the secret)
Set up 3 cups exactly as seen in Fig A
Flip over 2 cups at a time. Repeat this 3 times untill all three cups are down. (Fig B)
(almost any combination will work)
Now have volunteer try to duplicate this effect. It will be impossible.
The Gimmick: Arrange cups as below in Fig C. The volunteer will never notice.