Item Number: DV4281
Your Participant selects one of three authentic hotel room key cards and secretly writes an imaginary room number on the back. He holds that card number-side-down and slides it between the remaining two key cards. The three stacked cards are slowly and openly shown top and bottom, front and back. There is no doubt that all three hotel key cards are completely opaque and that the room number is totally hidden from view.
Yet you can reveal the secret information almost instantly!