The Gerber Convention

In the auction 1NT - 4♣, responder is asking how many aces opener holds. A strong balanced hand opposite a notrump opening often knows at once that the contract will be notrump and that slam is close. What it does not know is whether two aces are missing. Blackwood is no help here, because over a natural notrump bid 4NT is needed as a quantitative invitation. The Gerber convention moves the ace ask down to 4♣, a bid that is almost never needed as a natural call over 1NT or 2NT.

A jump to 4♣ directly over partner's natural 1NT or 2NT asks how many aces partner holds. The answers are steps, starting with the next bid up. After the answer, 5♣ asks for kings in the same way, and it promises that the partnership holds all four aces.

The structure is identical after a 2NT opening (20 to 21 balanced in most systems) and after a natural 2NT rebid, for example 2♣ - 2♦ - 2NT - 4♣.

The safest rule, and the one most club partnerships play, is short: 4♣ is Gerber only when it is a jump directly over a natural 1NT or 2NT bid. That covers the opening bids and natural notrump rebids. Everywhere else 4♣ keeps its normal meaning.

• 1NT - 4♣ and 2NT - 4♣: Gerber.
• 1♦ - 1♠ - 2NT - 4♣: Gerber for most partnerships, since opener's 2NT rebid is natural. Agree this one explicitly.
• 1♥ - 2♣ - 2♥ - 4♣: not Gerber. Responder has bid clubs, so 4♣ is natural, showing long clubs, or a cue bid.
• 1NT - 2♣ - 2♠ - 4♣: not Gerber for most pairs. A suit has been found, and 4♣ is a splinter or a cue bid agreeing spades. If you want to ask for aces in spades, use 4NT key card.
• After an opponent's bid: Gerber applies only if you play it explicitly in competition. Many pairs keep it off once the opponents have bid.

The player who bid 4♣ is the captain. After partner's answer, the captain has three choices.

1. 1.Sign off in notrump. The cheapest notrump bid, usually 4NT, is to play. When partner's answer is itself 4NT (three aces), the captain can pass or bid on.
2. 2.Bid a slam. Any bid at the six or seven level is to play.
3. 3.Bid 5♣, the king ask, when all four aces are held and a grand slam is possible. Partner answers in steps: 5♦ zero or four, 5♥ one, 5♠ two, 5NT three.

Neither answer counts your tricks. Knowing every ace and king tells you the opponents cannot cash two fast tricks, but not where thirteen tricks will come from. Before bidding a grand slam, count thirteen tricks in the two hands.

The deal is a useful reminder. Gerber confirmed every ace and every king, and seven was still wrong. If South had held a five-card diamond suit instead of the ♣8, 7NT would have been a good contract. To check a contract like this on your own deals, paste them into the double dummy solver.

• Using 4♣ when clubs might be natural. If partner's last bid was not a natural notrump bid, 4♣ is not Gerber.
• Answering every 4♣ as Gerber. Responder has to read the auction too. Over 1♥ - 2♣ - 2♥ - 4♣, partner has bid clubs twice, and 4♣ is natural.
• Bidding Gerber with a long, weak suit and unknown fit. Gerber is for hands that will play in notrump or that already know the trump suit. If you still need to find a fit, use Stayman or a transfer first.
• Signing off in 5♣. 5♣ is the king ask, not a sign-off. To stop, bid notrump at the cheapest level.
• Overruling the captain. After the 4NT sign-off, the notrump bidder passes, even with a maximum.

Some partnerships use Gerber more widely, for any jump to 4♣ when no suit has been agreed. Others use key card Gerber, which counts the trump king as a fifth ace in the way Roman Key Card Blackwood does. Acol players, with a 12 to 14 1NT, use Gerber in exactly the same way. Slams opposite a weak notrump are rarer, but the 4♣ ask works the same. If the opponents interfere, the DOPI and ROPI principles apply just as they do over 4NT. And many experienced pairs drop Gerber over 1NT altogether, using 4♣ and 4♦ as transfers to hearts and spades (South African Texas, a cousin of Texas transfers) and relying on quantitative bids instead.

What is the Gerber convention in bridge?

Gerber is a jump to 4♣ over partner's natural 1NT or 2NT that asks how many aces partner holds. Partner answers in steps, and a later 5♣ asks for kings. It leaves 4NT free as a quantitative slam invitation.

What are the responses to Gerber?

4♦ shows zero or four aces, 4♥ one ace, 4♠ two aces and 4NT three aces. After that, 5♣ asks for kings with the same steps, starting at 5♦.

When is 4 clubs Gerber?

In standard practice 4♣ is Gerber when it is a jump directly over partner's natural 1NT or 2NT opening or rebid. After a suit has been bid or agreed, 4♣ is natural or a cue bid.

What is the difference between Gerber and Blackwood?

Both ask for aces with step answers. Gerber uses 4♣ over notrump bids, which leaves 4NT free as a quantitative invitation. Blackwood uses 4NT once a trump suit is agreed.

How do you sign off after Gerber?

Bid notrump at the cheapest level, usually 4NT, which partner must pass. A bid of 5♣ is not a sign-off. It asks for kings.

Does Gerber apply over a 2NT opening?

Yes. 2NT - 4♣ asks for aces with the same step answers as over 1NT.