The No Bend Key is the ungimmicked version of the Easy Bend Key, this is just a regular key that is almost impossible to bend and looks identical to the Easy Bend Key.
As a routine idea, you can give the No Bend Key to a spectator, ask him or her to bend it, which if course they can't, you take the key back and place your hand on their forehead and tell them that you are giving him or her the power to bend it or to give them super strength or whatever patter you want to use. Whilst doing this, you are switching the key for an Easy Bend Key. You then give them the key and ask them to bend it as much as they can, which they can now do. You now say that you are going to take the power away and snap your fingers. Because the key is now bent, they of course can not now bend it back.