One-way decks: pattern reading

A one-way deck is a deck whose back design is not the same when you turn a card end for end. Line every card up the same way, and any card that gets turned around stands out to you while looking perfectly normal to everyone else. Magicians use that to find a chosen card after a shuffle. The principle is old and simple; the skill is in handling the deck so nobody ever thinks about which way the cards are pointing.

Why does the pattern on the back matter?

Most people never look at the back of a playing card. It’s just a pattern, and they assume every card is identical and symmetrical. That assumption is exactly what a one-way deck uses. If the design has even a tiny difference between its top and bottom halves, each card carries one bit of information: which way up it is.

One bit sounds like nothing, but it’s enough to find a selection in a shuffled deck, to tell which card was touched while you were out of the room, and to build a surprising number of tricks. In our guide to trick decks and which to buy first we compared the classic gimmicked decks by what they let you do. This post goes deeper into one quiet principle that sits underneath several of them.

What is a one-way deck?

A one-way deck has a back design that is not rotationally symmetrical, so a card turned end for end looks different from its neighbours if you know where to look. Some modern decks are printed with an obvious one-way picture on the back. Others use a tiny irregularity in an otherwise ordinary-looking pattern.

The same idea works on the faces. Many court cards and spot cards are not perfectly symmetrical, and magicians call these “pointer” cards. Professor Hoffmann noticed it in Modern Magic (1876): “the white margin round the court cards almost invariably differs in width at the opposite ends.”

One naming trap: a “one way forcing deck” is something completely different. That is a deck where nearly every card is the same card, and it has nothing to do with the orientation of the backs.

How does the one-way principle work?

The method has two parts. First, every card in the deck starts pointing the same way. Second, when the chosen card goes back, either the card or the rest of the deck is turned around, so the selection now points the opposite way to every other card.

T. Nelson Downs gave a full chapter to this in The Art of Magic (1909), using cards with a scroll design back and preferring “Angel Backs.” His point was that scroll designs contain small irregularities that nobody notices, but once you know where to look, “the slight differences in the design are as plain as a moon in a cloudless sky.” With the pack arranged one way, a card replaced the other way can be found however much the cards are shuffled.

Card cheats knew a version of this too. Jean-Eugène Robert-Houdin, in Card-Sharpers: Their Tricks Exposed (1863), pointed out that the designs on card backs are not always printed the same distance from the edges, and that cheats used the difference to recognise cards.

The stripper deck uses a related idea, except you feel the reversed card instead of seeing it.

When should you use a one-way deck?

• Finding a selection. A card is chosen, returned and shuffled in, and you find it by spotting the one card pointing the wrong way.
• Which card was touched? Hoffmann describes laying out four queens, leaving the room, and having someone turn any of them end for end while you’re gone. You can tell which one was turned. He even says that, against the usual rule, you may repeat it.
• Mind-reading presentations. Because you never need to touch the cards, the principle suits effects where you seem to sense a choice rather than find it.

It works best close up, where you can glance at the backs naturally. At a distance you can’t see the detail, and on stage the cards are too small to read.

How do you learn to use it?

The principle takes a minute to understand. The handling takes longer, and it’s worth being honest about that.

1. Train your eye. Spread the deck face down with one card reversed and practise finding it at a glance, without leaning in or pausing.
2. Keep the deck oriented. Every time you handle the cards, check that they all still point the same way. One stray card turned during an earlier trick gives you a false hit.
3. Practise the turn. Turning the deck around while the selection is being looked at must feel like nothing. Do it as part of a natural movement, not as a separate action.
4. Watch spectator shuffles. If someone else shuffles, their handling can turn half the deck around. Decide in advance whether you let spectators shuffle, and how you check the deck afterwards.

Reading old sources helps: Downs and Hoffmann both explain the setup in plain words, and their tricks still work. Their decks were different from ours, though, so check whether your own deck’s design is one-way before you rely on it.

Which products help?

• Elysian Duets Marked Deck (Red) by Phill Smith lists a new one way back and one way faces among its features, along with four corner marking, a double backer and a link to full online instructions and tricks.
• Diamond Marked Playing Cards by Diamond Jim Tyler has a subtle one-way element added to make locating a selection simple. It is also a marked deck, and includes a blank faced card and a double-backed card.
• The Art of Magic by T. Nelson Downs is a free public-domain ebook in our library. Chapter VIII is the one-way back chapter described above.

What are the common mistakes?

• Staring at the backs. If you study the deck, the audience studies it too. One relaxed glance is all you should need.
• Forgetting to reset. After a trick, the found card still points the wrong way. Turn it back before the next effect.
• Assuming every deck works. Many back designs are symmetrical. Test yours with two cards side by side, one turned around.
• Using it twice in a row for the same people. Hoffmann thought his four-card version could be repeated, but a full deck location is stronger once. Vary the method instead.
• Explaining too much. Never point at the backs or say the deck is ordinary. People only look for what you draw attention to.

Frequently asked questions