Source: http://www.vba.asn.au

Suppose you have a strong balanced hand in response to partner’s 1NT opening, and your thoughts turn to a possible slam. With a pair of balanced hands, you need to have a minimum of about 33 HCP collectively in order to make a slam. For example, if you have 16 HCP, then your combined HCP range is 32 to 34. You would like to know if partner is at the bottom or top of his range.

The way to find this out is to bid 4NT over 1NT. This is called a “quantitative” bid and asks partner to either pass with a minimum hand or bid 6NT with a maximum. This concept applies whatever the actual range of the 1NT opening.

The quantitative 4NT is the most underused bid in bridge.

You are probably used to playing 4NT as asking for aces, the Blackwood convention, and could legitimately ask what you are to do if you hold a hand where you do want to know the count of partner’s aces. The solution is the Gerber 4 bid. A response of 4 to a 1NT opening (or indeed a 2NT opening) asks partner to show how many aces he holds, via the same scheme of step responses that applies to Blackwood. So 4 would show 0 or 4 aces, 4 1 ace, 4 two aces, and so on.

Try out this scheme of responses on the following hands:

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(a)  KQ10  Q4  Q1052 AK86 4NT. A reasonable 16 HCP: if partner is at the high end of his range, you should have a decent chance to make 6NT.

(b)  KQ10  Q43  J852  AK8 3NT. Despite its 15 HCP, this hand has nothing going for it, with the sterile 4333 shape. Even if partner has 18 HCP, slam is uncertain.

(c)  KQ10  432  AQJ52  K8 4NT. This 15-count is much stronger than hand (b) because of the fine 5-card suit. It’s certainly worth a quantitative invitation.

(d)  KQ10  4  KQJ6542  A8 4. Gerber to the rescue. With the powerful 7-card suit, you just want to check that partner has at least two aces, and then you can bid slam. In fact, if partner has 3 aces, you should ask for kings (via a 5 bid), and should he have one, you can bid the laydown 7NT. After Gerber, 4NT by responder is a signoff.

(e)  K107  4  KJ6542  AK8 3. Slam all depends on whether partner has good diamonds for you. 3 shows a strong hand (a slam try) with at least 6 diamonds. If partner just rebids 3NT, you’ve had enough. But if he co-operates, you can bid 4NT which, second time around, does ask for aces.

(f)  KQ1076  4  KQ1052  A8 2 (transfer). Start showing your suits, first the spades, then the diamonds. If partner shows a fit for one of them, you’re off to the races. Without transfers, this hand is unbiddable.

Partner’s hand: AJ83  AKJ  97  QJ52 Have a look at how the auction pans out on each of the 6 hands above.