It is vitally important that defenders co-operate with each other to play their combined hands to best advantage. This is difficult because, unlike declarer, who can see both of his hands, defenders cannot see each other’s hands. To some extent this can be overcome by good “card reading” , i.e. noting inferences from the bidding and play which lead to conclusions about the strength and shape of the hidden hands. However, the most important way in which information is passed between defenders is the allocation of specific meanings to the play of each card, commonly called “signalling”. This starts, of course, with the opening lead and is the reason why there is a list of standard leads such as top of an honour sequence or fourth highest, etc. Subsequent to the opening lead, there are three messages which the defenders try to indicate to their partners by the specific cards played. These are “attitude”, “count” and “suit preference”.
On partner’s lead, assuming that you are not trying to win the trick but are merely intending to follow suit with a small card, the card you play should indicate to partner whether or not you would like the suit to be continued, either immediately or at a later opportunity. This is done by playing a moderately high card such as a 9 or 8 if you wish to encourage a continuation or by playing your lowest card if you wish to discourage a continuation of the suit led. This attitude signal applies not only on the opening lead but whenever a new suit is led by either defender.
962 Declarer plays the 2 from dummy. Play your 8 to
Lead: A Q83 encourage. It is likely that partner has the AK and you hope to make your Q on the 3rd round or force declarer to ruff.
Q92 Declarer plays the 2 from dummy. In a suit contract,
Lead: A 83 encourage with the 8 in the hope of a 3rd round ruff. In a NT contract, discourage by playing the 3.
Sometimes, on the opening lead and after dummy has been faced, it is obvious from the cards in view that the suit led should not be continued; perhaps, in a suit contract, dummy has a singleton in the suit led. Assuming that there are two suits which you do not want led, i.e. the suit led and the trump suit, say, the play of a moderately high card would suggest a switch to the higher ranking of the remaining two suits and a low card would suggest a switch to the lower ranking of the remaining two suits. This principle is known as a “McKenney” after the man who first suggested it.
When declarer plays his suits it is usual for the defender’s to indicate how many cards they have in the suit led. This is done by playing a highish card followed by a low card (known as a “Peter”) with an even number of cards and a low card followed by a higher card with an odd number of cards in the suit.
E.g. The contract is 3NT and there are no entries to dummy
9 other than in the suit shown. Partner’s 9 clearly
Lead: 4 KQJ852 indicates an even number of cards in the suit which
A76 must be two. Therefore, declarer has two and South must hold up his A for one round to prevent declarer gaining access to the long suit in dummy.
We have already seen that a secondary meaning of a card played to the opening lead may, under certain circumstances, be a McKenney suit preference signal. The McKenney principle, however, is much more commonly used when discarding. Whether in a suit contract or in NT, when about to discard, there are always two suits in which you have no interest. Firstly, there is the suit on which you are about to discard and, secondly, there is the suit which you are about to discard. That leaves two suits which you might wish to be led by partner at a later opportunity. In these circumstances, the discard of a highish card would suggest interest in the higher ranking of these suits and a low discard would suggest interest in the lower ranking of these suits.
Players are entitled, under the rules, to know what signalling system is being used by their opponents. Therefore, signals used by the defenders can just as easily be observed and translated by declarer, possibly to the disadvantage of the defenders. However, it is generally regarded as more important to keep your partner informed than to withhold information from declarer but, obviously, there are occasions when it pays to deceive declarer, albeit at the risk of confusing partner.