Business card puzzle
You place a number of white cards side by side on the table, ask a spectator to write their name on one of them, and then turn it over. Then he should push the cards together and shuffle them.
While the viewer is doing this, turn away or leave the room. After the spectator has thoroughly shuffled the cards, they are placed back next to each other on the table. Then put your autograph on one of the cards and give it to the spectator as a souvenir. If he turns the card over, he sees that you wrote your autograph on the very card on which he previously signed!
This effect is based on an ingenious trick principle that cannot be deciphered. It was one of the favorite feats of the great Fred Kaps.
You will receive a set of cards (size 6 x 9 cm) and German instructions.