Suit Preference Signals: Lavinthal and McKenney Explained

A suit preference signal is a card that tells partner which of two other suits you want him to lead: a high card asks for the higher-ranking suit, a low card for the lower-ranking one. The suit being played and the trump suit are left out, so only two suits are left to choose between. In North America it is called the Lavinthal signal, after Hy Lavinthal, and in Britain the McKenney signal, after William McKenney; it is the same idea.

Suit preference is the third signal, after attitude and count, and it has the narrowest use: it applies only when the other two signals would tell partner nothing he needs. When it does apply, it often decides the deal, because it shows partner the way to your entry.

Take out two suits: the trump suit and the suit being played. The two that remain are ranked:

Against notrump there is no trump suit, so three suits remain besides the one being played. The context removes one more, usually the suit declarer is clearly going to play, such as dummy's long suit, and leaves two to choose from. Many pairs also agree that a middle card shows no preference or asks partner to continue the same suit.

A signal is relative. The ♥6 is high from ♥6-3-2 and low from ♥K-J-8-6. Partner reads it by looking at the cards he can see: dummy, his own hand and the cards already played.

These are the common situations, from the clearest to the ones that need agreement:

1. Giving partner a ruff. The card you lead for him to ruff shows where your entry is, so he knows what to return for the next ruff.
2. Clearing a long suit against notrump. When the suit is set up and partner must find your entry later, the spot card you play on the clearing round shows where that entry is.
3. Following to a suit that partner will obviously ruff or that cannot matter, such as when dummy has a singleton and partner leads the ace. Many pairs treat the card as suit preference here. Agree it.
4. Lavinthal (McKenney) discards, if you play them: your first discard shows which of the other two suits you want.
5. Trump suit preference. Some pairs give suit preference with their small trumps when count in trumps cannot matter. Again, an agreement.

What it is not: on partner's normal opening lead, your card is attitude. On declarer's lead in a long suit, it is count. Do not read every card as suit preference, or you will see messages partner never sent.

You lead your singleton ♦5, partner's suit. Partner wins the ♦A and returns a diamond for you to ruff. Which diamond he returns is the whole deal.

Partner holds the ♣A, so he returns his lowest diamond, the ♦3: a low card asks for the lower of the two side suits, clubs, rather than hearts. You ruff and lead the ♣J. Dummy's ♣K-Q are beaten by partner's ace, and partner gives you a second diamond ruff. Diamond ace, ruff, club ace, ruff: 4♠ goes one down.

Double dummy, everything hangs on your switch after the first ruff:

Without the signal, the heart switch looks natural: dummy's clubs are K-Q-5, and your ♥J-10-9 sequence is a safe lead. If partner had held the ♥A instead, he would have returned a high diamond, such as the ♦10, and you would have switched to hearts.

Against 3NT, you lead the ♠K from ♠K-Q-J-8-3-2. Declarer ducks the king and the queen and wins the third round with the ♠A. Dummy's long suit is diamonds, so declarer will attack them next, and if partner wins a diamond he must know how to reach your spades.

The third round is your chance. The ace will win that trick whatever you lead, so the spade you choose carries no other message. Lead the ♠8, a high spot, to say "my entry is in hearts", the higher of the two suits left once spades and diamonds are taken out. Lead the ♠2 to say "clubs".

Partner, holding say ♦A-x, wins the first diamond and returns the suit you asked for. You win your ace and cash the spades. Without the signal, he would have to guess, and against a good declarer, half the time he would guess wrong.

This use needs no special agreement: once your suit is set up, its spot cards have no other job, so they are free to show the entry.

With Lavinthal discards, your discard says "I do not want this suit", and its size shows which of the other two suits you do want. A high discard asks for the higher-ranking of the two, a low discard for the lower.

Example: against 4♠, declarer draws trumps and you have to discard. You want a diamond lead and you hold small clubs and long hearts. The other two side suits, apart from clubs, are hearts and diamonds. Discard a low club: it says "not clubs, and of the other two, the lower one", diamonds. A high club would ask for hearts.

Against notrump the rule is the same, with the suit declarer is running left out: if declarer runs diamonds and you discard a club, a high club asks for spades and a low club for hearts.

The advantage over attitude discards is that you never have to throw a card from the suit you want. The disadvantage is that every discard carries a message, even when you are just throwing a useless card. Some pairs prefer odd-even discards for that reason. Whatever you play, use it with upside-down signals or standard signals in the other situations; the suit preference rule itself does not change.

• Signaling suit preference on partner's opening lead. On a normal lead, partner wants attitude. Only in the special situations above does the card change meaning.
• Forgetting that trumps are left out. When hearts are trumps and you return a spade for a ruff, a high spade asks for diamonds, not hearts.
• Using a card you need. From ♦Q-10-9-4-3, the ♦Q may be a trick later. Signal high with the 10 or the 9 when the queen matters.
• Making the signal ambiguous. If partner cannot tell your card is high, it is not a signal. Use your highest or lowest spot, not a middle card, when the message matters.

To see these signals work on real deals, replay hands in the double dummy solver and check what each defender should have played. For the other signals, read bridge signals and the beginner lesson on defensive signals; for leads, start with opening leads.