The magician selects a card from the deck, which is kept secret from the spectators. He folds it into quarters, with the back outermost, and places into the grip of a bulldog clip. He explains that this card is a prediction.
A spectator then picks a card from the deck and signs it on the face. The card is returned to the deck and the deck is shuffled. The magician now draws attention to the bulldog clip once again, which has been in full view for the whole trick - he picks it up, removes the folded card from it's grip, and unfolds it. It is the spectator's signed card.
