I have an idea that both conventions are used to check for aces in slam bidding, and that one starts at four clubs and the other at 4NT. Beyond that, I'm confused.

Why would a bidder use one over the other? Or is it that some systems prefer one over the other?

How would I tell which one my partner is using? Or must we agree beforehand?

  • Yeah, Blackwood and Gerber are for different things. You might want to check out variants of Blackwood, like Roman Key Card Blackwood, for different approaches to seeking a fit for slam. – thesunneversets Jun 9 '11 at 16:21

Blackwood is used for suit contracts, while Gerber is used for Notrump contracts. This was a necessary evil based on how Blackwood develops.

Say we have established that we should be in Notrump, and I want to try for slam. If I bid 4NT Blackwood, and find out that we are missing 2 Aces, how can I sign off? 5NT would ask for Kings, and 6NT is obviously too high. There's no way to bid a safe level of Notrump anymore. By using the Gerber 4C bid, I can sign off in 4NT if we are missing two aces.

  • OK. You can't use NT to check for NT. So you use Gerber, instead. – Tom Au Jun 9 '11 at 15:44
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    You could use 5S as a signoff to 5NT. I believe we don't use 4NT as Ace asking in response to 1NT or 2NT because that is used as a quantitative bid. And 4C in response to a suit is better used as a splinter/other bid. – Aryabhata Jun 9 '11 at 17:41
  • True, 5S as a conventional transfer would have as good a solution as anything to solving this problem. I think (but don't know for sure) that the quantitative 4NT was created after we stopped using Blackwood for Aces over Notrump. – dpmattingly Jun 9 '11 at 17:47
  • Maybe you are right, it would be interesting to find that out. – Aryabhata Jun 9 '11 at 17:52
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A significant drawback of Gerber is that it interferes with cue-bidding sequences. Gerber is now seen as rather old-fashioned, although you will still find plenty of people who play it. It does have the virtue of keeping the bidding at a lower level if you don't get the answer you're looking for.

  • Welcome to the site. Thanks for your answer, which I have upvoted. – Tom Au Sep 2 '11 at 12:55

Lesson 5 of the ACBL website's Teachers' manuals give a comprehensive explanation of Gerber and Blackwood conventions with lots of examples.

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    Hi Rosemary, welcome to the site. While somewhat useful, your answer would be much better if you linked to the resource you describe, and if you summarised the information available there. Can you answer the OP's questions based on the content of your manual? – ire_and_curses Jun 7 '13 at 22:04

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