Bridge Lesson 21: Bidding a Slam With Blackwood

Bid a small slam, twelve tricks, when your side holds about 33 high-card points, or about 30-31 with a good trump fit and shape, and you are not missing two aces. Bid a grand slam, all thirteen tricks, with about 37 points or when you can count thirteen tricks. Blackwood, a 4NT bid that asks partner how many aces they hold, is the simplest way to check the aces before you bid six.

Slams pay well at duplicate: a small slam adds 500 not vulnerable and 750 vulnerable, a grand slam 1000 and 1500. But a slam that goes down scores less than the game you passed, so the checks matter.

The deck has 40 high-card points, and the numbers follow from that:

Why 33? With 33, the opponents hold at most 7, so they cannot hold two aces, which are worth 8. Why 37? Then they hold at most 3, so they cannot hold an ace at all.

A good fit and short suits replace points. With a nine-card trump fit and a singleton, 30 or 31 points often make twelve tricks, because ruffs take the place of high cards. Count your dummy points from Lesson 15 when you look for a slam in a suit.

Once you know the trump suit and you think the side has enough for slam, bid 4NT. Partner answers with the number of aces:

You can see what 4NT means in every system.

Add partner's aces to yours. Missing two aces: sign off in five of your trump suit, and partner must pass. Missing one: bid six. Holding all four, you may bid 5NT to ask for kings (6♣ = 0 or 4, 6♦ = 1, and so on) on the way to a grand slam. 5NT promises all the aces, so never bid it without them.

Most tournament players use a stronger version, Roman Key Card Blackwood, which counts the king of trumps as a fifth ace and also asks about the trump queen. Learn the plain version first; the logic is the same.

Blackwood tells you how many aces partner has, not which ones, and nothing about the other suits. Do not use it when:

1. You hold a void. Partner's ace in your void suit is wasted, and the answer cannot tell you which ace partner holds.
2. You have two fast losers in a suit nobody has bid, such as two small cards. Partner's aces may be elsewhere. Show your controls with cue bids instead, or ask partner to.
3. Clubs are trumps and you hold only one ace. If partner answers 5♦, you are missing two aces and already past 5♣.
4. Partner opened notrump. Then a direct 4NT is a natural slam invitation, not Blackwood; the ace question over notrump is the Gerber convention, 4♣.

Blackwood keeps you out of a slam that is missing two aces. It does not tell you whether a slam exists.

You hold 20 HCP with five hearts and a singleton spade. Partner's 3♥ is a limit raise: 10-12 dummy points with four hearts. Your 20 plus partner's 10-12 is 30-32, and the fit and your singleton make up the rest. Hearts are agreed and you have no void, so Blackwood is the right tool.

You hold two aces. Partner's 5♦ shows one more, so the opponents have one: bid 6♥. Partner holds 11 HCP, the ♦A among them.

Double-dummy analysis gives 6♥ by South twelve tricks. The only loser is the ♣A: after your ♠A, dummy's ♠K and ♠Q are winners, and they take care of two of your diamonds.

For cue bids, grand slams and the full method, continue with slam bidding once this course is done.

Slam hands are rare, so most players get little practice with them. BridgeDummy bidding puzzles let you pick a call in a set auction and then show how every option scores over many deals that fit it, which is a quick way to learn when six pays and when it does not.

Previous lesson: Lesson 20: Preempts. Next lesson: Lesson 22: Overcalls. Full course: Bridge lessons for beginners.