Read main articles: Contract bridge and Glossary of contract bridge terms
In the card game of contract bridge, partners defending against a contract may play particular cards in a manner which gives a coded meaning or signal to guide their subsequent card play; also referred to as carding. Signals are usually given with the cards from the two-spot to the nine-spot. There are three types of signals:
The methods used for each type of signal have evolved over time and fall into two broad categories:
|Lead is by||Following suit||Discarding|
2. suit preference
2. suit preference
Partnerships decide on which methods to adopt and must disclose them to their opponents. Use and interpretation is dependent upon their context, i.e. the contract, the auction, the opening lead or prior play, the cards visible in dummy, the cards visible in one's hand, who has led to the current trick and whether following suit or discarding.
Accordingly, partnerships generally have an order of precedence for the interpretation of signals such as that indicated in the adjacent table. In the vast majority of cases, the third-hand follow-suit signal is an attitude signal, but when the attitude signal does not apply, it is a count signal. Usually, it is relatively easy to recognize a signal correctly when the declarer leads - either a count signal when following suit, or an attitude signal when discarding, and when they do not apply, it is a suit-preference signal.
While signals are a means of permissible communication between defenders, they are considered as providing guiding information to partner and are not absolutely binding on him; partner may proceed otherwise as he deems rationally appropriate. Because declarer is entitled to know the meaning of all partnership agreements, including defenders' signals, he also is privy to the information being exchanged; this may give way to falsecarding tactics by the defenders.
When signaling standard attitude, a high card is encouraging and a low card is discouraging. Attitude is normally signaled when following suit to partner's led suit and when discarding on either partner's or declarer's led suit.
For example, if partner leads the Ace of spades, you might signal with the nine if you held the King (requesting partner to continue the suit), or with the three if you held nothing but small cards in spades (notifying partner that a switch to another suit is likely best).
Of course, you can only signal with the cards you hold. Signaling low is easy for you, but if your lowest card is the eight, partner might have difficulty "reading" it as low. When you are signaling high, play the highest card you can afford. Having easily readable cards to signal with is part of the luck of the deal.
Suppose declarer is drawing trumps and you are out on the third round. Your discard should be an attitude signal for partner. If you play a high diamond, for example, you ask partner to lead diamonds if she should gain the lead. Normally, you would have an honor or honors in diamonds in this case. If you play a low diamond, you ask partner to not lead diamonds if she should gain the lead. Partner will usually be able to figure out which of the other suits you do like (if any).
If declarer plays yet another round of trump, you may be able to play yet another diamond. This will make it unambiguous to partner whether you are encouraging diamonds (by playing high-low) or discouraging diamonds (by playing low-high).
With standard attitude signals you generally play the highest card you can afford for that purpose. Typically attitude signals are made when partner leads an honor (either on the opening lead or later) and requests a continuation. The usual reason for this is that you possess an honor equal to the honor played or promised by the lead. Against a notrump contract (especially on the opening lead) partner will lead an honor from a solid or broken sequence, such as QJ10 or KQ10. With less solid holdings like QJxx(x) or KQxx(x) partner will lead his fourth best card. The reason to signal is, if partner leads from a broken sequence and there are small cards in dummy, partner may not know whether to continue the suit (should the trick hold or they gain the lead before you).
|K Q 10 6 2||W N↑ S↓ E||J 8 3|
|A 9 5|
Partner leads the king against a notrump contract, with your J83 you would play the 8. So if partner has something like KQ1062 and declarer A95 they can continue the suit without giving up a trick if declarer lets it hold.
|K Q 10 6 2||W N↑ S↓ E||9 8 3|
|A J 5|
If you play the 3 partner may take this view of the suit, and may switch to another suit hoping to get you in to lead though declarer's probable jack. It is also possible that you have the singleton or doubleton 8, but in that case declarer would have 4 or 5 cards in the suit and the bidding may have revealed that. If declarer had bid the suit, your partner would also be less likely to lead from a broken honor sequence or maybe even lead the suit at all.
Note that some players agree to unblock their highest honor when a King is led against a notrump contract, and with no honor to give a count signal.
The general principle is to not signal if doing so will help declarer more than the defenders.
Case 1: You judge that you hold virtually all of the defensive cards, that partner will very probably never gain the lead. Do not signal. Partner, on the other hand, knowing the situation, should consider signalling honestly.
Case 2: Signalling against a slam is very dangerous. Make declarer work as hard as possible.
The standard count signal is to play high-low with an even number of cards, and low-high with an odd number. Normally, you "give count" when following suit to declarer's led suits. This will help partner determine the distribution of the suit. See duck (bridge) for an example.
Count in the trump suit is normally inverted. Thus, high-low shows an odd number of trumps (probably three). Some partnerships (by advance agreement) signal this way only when they have a desire or ability to ruff something.
This signal is used infrequently. When it is clear that the choice of lead is between two suits, the play of a high card on a previous trick suggests the lead of the higher-ranking suit and a low card suggests the lower-ranking suit. There are four common cases:
Some partnerships agree in advance to play UDCA. With this agreement, the standard count and attitude signals are inverted: when signaling attitude, a low card is encouraging and a high card is discouraging; when signaling count high-low shows odd count, low-high shows even count.
Many experienced players believe UDCA is superior to standard signaling. Most importantly, it is often easier for partner to read your signals. Also, you do not have to "waste" high cards in suits you like.
Caution: UDCA, as the name states, applies to count and attitude signals only. Suit preference signals are played standard. Also, your leads (as opposed to signals) are unchanged - you still lead high from a doubleton, for example, barring another special agreement to the contrary.
As mentioned above, standard count in the trump suit is already "upside down". Experts recommend that trump signaling be the same in UDCA as standard trump signaling, that is, when playing UDCA, signal the same in all four suits.
Some partnerships agree in advance to assign special meaning to the first discard.
With this agreement, the first discard is suit preference. You do not like the led suit, of course, and you do not like the suit discarded. Your suit preference signal tells partner which of the two remaining suits you prefer. A high card for the higher ranking of the remaining suits and a low card for the lower ranking. This treatment is known as Lavinthal in the United States, or McKenney in the UK. The potential disadvantage of this method is that you always have to give preference for one suit or other, and you may not want any switch in particular. This can be overcome at times by signalling for an "impossible" switch, such as a suit in which dummy has a very strong holding e.g. AKQ.
There is another slightly different Lavinthal used by SAYC OKBridge Style Simplified: discard of a low card of either remaining suit (i.e., excluding trumps and the suit you are out of), asks for the lower suit. For example, if hearts are trumps and you are discarding on clubs, then a low spade or diamond asks for a diamond. Discard of a high card of either remaining suit, asks for the higher suit.
As with Lavinthal, you have the possibility to request suit preference in two ways. A low discard indicates interest in the suit directly below (a low club signaling spades); a high discard signals preference for the suit directly above (a high spade signaling clubs). In a suit contract, the trump suit is skipped in reading the signal. This is felt by many to be easier to remember than Lavinthal.
With this agreement, the first discard shows the following: if it is an odd spot card (three, five, seven or nine) it is encouraging in that suit; if it is a low even spot card (deuce or four), it is suit preference for the lower ranking suit of the other two suits; if it is a high even spot card (six or eight), it shows preference for the higher ranking suit. The even card often has a dual function, in that, it not only indicates suit preference but it is also a negative indication for the suit being used for the even card. A high odd card followed by a low odd card may show both preference and count (odd or even number of cards, depending on partnership agreement).
A surrogate suit is one played by declarer in which a defender has neither need to signal his attitude or count nor use to give a preference signal; usually the trump suit is a good surrogate suit if a trump echo is not needed. The suit in which the count will be given is called the target suit.
Declarer is entitled to know what signaling agreements you have with your partner, and you must disclose them if asked. However, you do not have to interpret any particular play (and should not, because it might transmit information to your partner). For example, if partner plays the 5 of clubs and you are asked what it means, you should simply say "a high club encourages clubs, a low club discourages clubs" (assuming that is your agreement). If you see the 4, 3, and 2 in your hand, you know that the 5 is a low club and therefore discouraging, but you should not say so. As far as your partner knows it might equally well be declarer who holds those cards and then you might misread the 5 as encouraging.
Most regulating bodies in bridge also prohibit the use of encrypted signals. These signals convey a message that can only be interpreted by knowing some specifics of the hands of the defenders. For example, declarer's bidding might promise exactly a certain number of spades. By looking at the dummy, each defender knows how many spades the other has. An agreement applied in such circumstances, such as "if I have an even number of spades at the start of play, then we play standard signals on this deal, otherwise upside-down signals" would be encrypted and therefore widely prohibited.
In general, the partner will gain more from a player's signals than declarer, so it is worthwhile to signal honestly most of the time. However, since declarer can see your signals as well, a player who gains a reputation for always giving accurate count, for example, may find information given away by their signals used to their disadvantage. So it is common practice to throw in a misleading signal now and then, hopefully when it won't matter to partner.