The Gerber Convention

Four clubs, because over a no-trump bid 4NT has a better job to do.

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Four Clubs, Over No Trumps Only#

Gerber is a bid of 4♣ directly over partner's no-trump bid, asking how many aces they hold. It is artificial: it says nothing about clubs, and partner must not pass it.

It exists for one reason, and the reason is 4NT. Over a no-trump opening, partner has already described a narrow balanced range in a single bid, which makes 4NT far more valuable as a quantitative invitation — "bid six if you are at the top of your range" — than as an ace ask. Gerber takes the ace-asking job and moves it down to 4♣, leaving 4NT free to mean what it is better at meaning.

That is the whole trade, and it is worth seeing clearly: you are not gaining an ace ask, you are relocating one, in order to keep a natural bid natural.

The Four Replies#

Opener answers in steps, starting at 4♦:

Rase's robots reply on exactly this ladder. Like every step response it is artificial — 4♥ is not a heart suit, and correcting it as though it were is the commonest way these auctions go wrong.

The first step carries two meanings, and in practice that costs nothing. If you are asking for aces at all you hold a strong hand, and a partner who opened a limited no-trump cannot also hold all four aces unless you hold none — so count your own first and the answer reads itself. The ambiguity only bites on hands that were never going to arise.

It Is Not Gerber After a Suit Auction#

This is the trap, and it is the one that costs a contract rather than a part-score. 4♣ is Gerber only when partner has actually bid no trumps. In an auction that has been about a suit, 4♣ is a cue-bid or a natural club bid, and treating it as an ace ask means passing an artificial reply in a suit nobody holds.

Rase's engine gates it precisely there: it reads 4♣ as Gerber only when the partner being asked has a no-trump bid of their own in the auction. Everywhere else the call keeps its natural meaning.

The practical form of the rule is short enough to remember at the table: no no-trump bid, no Gerber. If you want aces after a suit auction, that is what Blackwood is for, and key-card Blackwood will tell you about the trump king besides.

Ask Only When the Answer Can Change Something#

An ace ask is not curiosity. It is the last question before a slam decision, and it is worth asking only when you already believe the slam is there and are checking that you are not off two cashing aces.

Rase's robots use roughly game values plus another eight points before they reach for 4♣ over a 1NT opening. Below that the hand belongs in game, and the ask does nothing but tell the defence that one side is short of aces while pushing the contract a level higher.

The discipline that follows is the one people skip: if the answer can never stop you, do not ask. A hand determined to bid the slam whatever partner replies should simply bid it.

On in ACOL, Off in 2/1#

Gerber is on by default in ACOL and off in 2/1.

With the switch off, Rase's robots put 4NT over a 1NT opening to the quantitative use instead — a slam invitation opposite the top of the range, rather than an ace ask. That is a coherent pairing, and it is why the two settings move together: the convention and the natural bid it displaces cannot both own the same call.

So the choice is not really "do I want Gerber" but "over a no-trump opening, which question do I more often want to ask — how many aces, or are you maximum?" Playing 2/1 here, the app answers the second. Playing ACOL, the first.