Your partner makes an opening lead. The dummy comes down, the declarer plays a card from the dummy, and suddenly it’s your turn to play, making you third hand. By the time you have to play, you've heard the bidding and seen your partner’s opening lead, and you’ve seen the dummy.
Your partner will lead either a low card, typically fourth highest from her longest suit, or an honor card, top of a sequence. Your play depends on whether your partner leads a low spot card or an honor card, and what you see in the dummy.
When your bridge partner leads a low card and the dummy has only low cards
When your partner leads a low card and the dummy has only low cards, play your highest card. Third hand high is an easy term to remember, and playing third hand high is a great defensive rule.
To understand the idea behind playing third hand high, think about your partner’s opening lead. You know that your partner has an honor in the suit because she led a small card. Therefore, you play the third hand high to protect your partner and prevent the declarer from winning a cheap trick.
When you have two or three equal honor cards
When you have equal high cards (such as the KQ, QJ, J10, or 109) in the third seat, play the lower or the lowest equal. This method of playing the lower or lowest equal in the third seat is a universal agreement. The whole world does it this way! By playing the lower or lowest equal, your partner can often tell what cards you don’t have! For example, if you play the king, you can’t have the queen. If you play the queen, you can’t have the jack, and so on.
When third hand plays by the rules, the opening leader can deduce who holds certain cards. For example, knowing that third hand will play the lower of equals allows the opening leader to image out who has the missing ♠K in this image.
You (as West) lead the ♠2, the dummy plays low, and your partner (as East) plays the ♠A. Who has the ♠K? Well, you don’t have the ♠K, and the dummy doesn’t have it. If your partner has the ♠AK, the proper play is the ♠K, the lower equal. When she plays the ♠A, she’s practically shouting that she doesn’t have the ♠K. Elementary, my dear Watson.
When you have both a lower and a higher honor card than the dummy
The dummy doesn’t always have just low cards. Sometimes the dummy comes down with an honor (or two) in the suit your partner leads, but you may happen to have a higher and a lower honor than the dummy’s honor.
Say that your partner leads a low spade, and the dummy tables with an honor in spades. You, the third hand, have a higher and a lower spade honor card than the dummy. What to do? It’s simple:
If the dummy plays low, play your lower honor. When the dummy plays low, you keep the honor that’s higher than the dummy’s honor, to zap it later.
If the honor is played from the dummy, cover with your higher honor.
Holding back your higher honor doesn’t always win the trick for you. Sometimes the declarer has a higher honor than your honor. Take a peek at this image.
Your partner leads the ♠2, the dummy plays low, and you correctly play the ♠J. But this time, the declarer (South) takes the trick with the ♠K. Don’t despair — despite this momentary setback, you’ve made a good play.
If you had erred by playing the ♠A, the declarer would have taken two later tricks with the ♠Q in the dummy and the ♠K. This way, though, the declarer takes only one trick, the ♠K.
When your bridge partner leads an honor card
Your partner may lead an honor card, thus suggesting a sequence in the suit. The lead of an honor card shows a sequence of three equal (consecutive) honors, or the third card in the sequence can be missing by one link. For example, the KQJ and the KQ10 are considered sequences; the KQ963 is not considered a suit headed by a sequence.
Your partner can lead five possible honor cards: the ace through the 10. Each honor card lead suggests a different holding:
The ace: Shows a suit headed by the AKJ or the AKQ.
The king: Shows a suit headed by the KQJ or the KQ10.
The queen: Shows a suit headed by the QJ10 or the QJ9.
The jack: Can show a suit headed by the J109 or the J108, or a suit headed by the AJ10 or the KJ10.
The 10: Are you ready for this? The lead of the 10 shows suits headed by the 1098 and the 1097, as well as suits headed by the A109, the K109, or the Q109.
When your partner leads an honor card, you may have one of the following holdings in your partner’s suit:
An honor equal to the one your partner has led
A higher unequal honor
Any doubleton honor (two cards headed by one honor card)
No honors (bummer)
When your bridge partner leads an honor and you have a higher honor than the dummy
Frequently, when your partner makes the opening lead of an honor card, the dummy also has an honor card, but on a good day, you have a higher honor than the dummy’s honor. Take the cards in this image as an example.
Your partner leads the ♠10 (top of an interior sequence), the dummy plays low, and you have a higher honor than the dummy, but no lower honor. Play the ♠7, your highest spot card and let your partner’s honor card do the dirty work of driving out the declarer’s honor card.
When your bridge partner leads an honor card in your suit
During the bidding, you may have mentioned a suit, and your partner may lead that suit. If your partner leads an honor card that’s going to take the trick, give her either an encouraging signal (play a high spot card), if you want the suit continued, or a discouraging signal (play your lowest spot card), if you want your partner to lead another suit.
As the player who makes the lead, pay attention to your partner’s signal. Even though your partner has bid a suit and you lead a winning card in that suit, your partner will tell you whether to continue the suit or whether to switch to something else.