A card (with a picture of the great Houdini) is locked inside a see cut-out frame with a nut and bolt.
It is impossible for “Houdini” to escape without removing the bolt. The magician unbolts and takes out the card from the frame to show that this is the only way for the card to come out from the frame.
The magician puts back the card into the frame and locks it again with the bolt. He pulls the card again to show it is locked in the frame. He tells the audience that he is going to take them back in time to show them how Houdini used to escape.
“Houdini just used magic” he says, pulling out the card to every one’s amazement.
Magician then hands over the card, the bolt and the frame to the audience to check.