Forcing Decks are a type of Mechanical Deck of playing cards used to force a spectator to select a particular card, which the magician knows in advance.
Forcing Decks can be divided into two kinds.
- Those which can help you force a particular card or know exactly which card the spectator selected
- Those which help force a group of cards, but the magician must then "pump" the spectator for a bit more information to determine the card.
The simplest forcing deck is one in which all cards are identical. In this instance, the magician must be careful to prevent the spectator seeing the faces of the cards.
A two-way forcing deck consists of two sets of identical cards, one set comprising the top half of the pack and the other the bottom half. A deck of this nature can be used to force two different cards on two spectators. Similarly, a three-way forcing deck is comprised of three different sets of identical cards.
A 50/50 forcing deck is a deck in which the top half is made up of the same card and the bottom half is composed of indifferent cards. Providing he only shows half of the deck, the magician can fan the cards face-up to supposedly demonstrate that all cards are different. When offered to the spectator for selection, he must ensure that he or she selects a card out of the top half.