Gerber Convention: Asking for Aces Over Notrump

Gerber is a jump to 4♣ over partner's notrump bid that asks how many aces he holds. Partner answers 4♦ with zero or four, 4♥ with one, 4♠ with two and 4NT with three.

It does the same job as Blackwood, one level lower. That matters in notrump auctions: after 1NT - 4NT, the 4NT bid is already used as a quantitative invitation, and if you ask with 4NT and get a bad answer you have nowhere to stop. With Gerber, you can still sign off in 4NT. John Gerber of Houston introduced the idea in 1938, and it is common in Standard American, 2/1 and Acol club play.

Partner opens 1NT or 2NT. You jump to 4♣. Partner counts his aces and answers in steps:

As with Blackwood, the zero-or-four answer is never really in doubt. If you hold an ace, partner cannot have four. If you hold none, a notrump opener with zero aces is still possible, but the rest of your hand and his range will tell you which it is.

You are the captain. Partner gives the number and then passes whatever you bid next, unless you ask another question.

Gerber causes more partnership accidents than any other convention, and almost all of them come from one question: was 4♣ Gerber or not? The safe, common rule:

4♣ is Gerber only when it is a jump directly over partner's natural notrump bid, such as 1NT - 4♣, 2NT - 4♣, or 2♣ - 2♦ - 2NT - 4♣.

In other auctions, 4♣ has its normal meaning:

• After a suit is agreed, 4♣ is a control-showing cue bid. In 1♥ - 3♥ - 4♣, opener shows a club control and slam interest in hearts.
• When clubs have been bid naturally, 4♣ is a raise or a natural rebid.
• After Stayman or a transfer, many pairs treat 4♣ as a cue bid or a splinter, because a fit has been found.
• Over a gambling 3NT, 4♣ usually says "pass or correct to your minor".

Some partnerships extend Gerber to any 4♣ bid over any notrump bid, including 3NT. That is a valid agreement, but write it down: the default in most clubs is the direct jump only.

Once you know the aces, you place the contract:

• Two aces missing: bid 4NT. Partner must pass. (If partner's answer was 4NT, showing three aces, you are already there and can pass.)
• One ace missing: bid 6NT, or six of your long suit.
• No aces missing: you can ask for kings with 5♣.

The king answers follow the same steps: 5♦ = 0 or 4 kings, 5♥ = 1, 5♠ = 2, 5NT = 3. The 5♣ king ask promises that your side holds all four aces, so partner knows a grand slam is the question.

A bid of 5NT, 6NT or 7NT after the answers is to play. A new suit at the five level is natural in most partnerships, but agree it first.

You are South with ♠K5, ♥KQJ, ♦KQJT85, ♣Q3: 17 HCP and a six-card diamond suit with no ace. Partner opens 1NT (15-17). Your side has at least 32 HCP and a source of tricks, so slam is likely, but you hold no aces. If partner has only two, the defense can take two aces against any slam. One question settles it, so you bid 4♣ (see what 1NT - 4♣ means in every system).

Partner shows three aces: the ♠A, the ♥A and the ♦A. The defense has only the ♣A. Declarer has three spade tricks, four hearts and six diamonds, so the defenders must cash the ♣A at once, and they take nothing else. 6NT makes.

Now suppose the ♥A is with the opponents and partner makes up his points with honors elsewhere. He answers 4♠, two aces. You bid 4NT, and partner passes. Without Gerber you would have had to guess, and a guess of 6NT would go down when the defense cashed two aces.

Why notrump and not diamonds? With 34 HCP between two balanced-looking hands, 6NT scores more than 6♦ at matchpoints and is just as safe here. If you were missing a stopper in a side suit, you would choose the suit slam.

1. Using Gerber in a suit auction. Once a suit is agreed, 4♣ is a cue bid, and 4NT is the key card ask.
2. Using Gerber with a balanced 18-19 count. When your strength alone guarantees that partner holds most of the aces, Gerber adds nothing. Bid 6NT; the quantitative 4NT invite is for a hand of about 16-17.
3. Passing partner's answer. The 4♦, 4♥ and 4♠ answers are artificial. Never leave partner there.
4. Partner bidding on after the 4NT sign-off. The asker has decided. Pass.
5. Asking for kings with an ace missing. 5♣ promises all four aces.
6. Confusing Gerber with Texas. Over 1NT, 4♦ and 4♥ are often Texas transfers. 4♣ stays Gerber. Pairs who play South African Texas use 4♣ as a transfer to hearts, so they give up Gerber at that point.

• Roman Gerber: 4♦ shows zero or three aces, 4♥ one or four, and 4♠ two.
• Key Card Gerber: when a suit has been agreed, some pairs use 4♣ as a key card ask with the 1430 answers, counting the trump king as a fifth ace. It is most useful when a minor is trumps, where 4NT answers would go too high.
• Gerber over any notrump bid, including 3NT rebids and 1NT overcalls, by agreement.
• Kings by number or by suit: most club players count kings after 5♣; some experts show specific kings.

If your partnership already plays Roman Key Card Blackwood in suit auctions, the simplest plan is plain Gerber over notrump openings and RKCB everywhere else.

The fastest way to make the Gerber rule automatic is to see it in many auctions. In the BridgeDummy Bidding Room you bid random deals with EPBot robots and review the full deal afterward, so slam hands opposite 1NT come up on their own. For close notrump slams, the free double dummy analyzer shows exactly how many tricks 6NT and the suit slam take on any deal you enter.

• Blackwood convention: the 4NT ace ask for suit auctions.
• Roman Key Card Blackwood: key cards and the trump queen.
• Slam bidding: the quantitative 4NT and other slam tools.