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The Blackwood Convention

The Blackwood Convention is a bridge convention used in slam bidding. A 4NT bid after trumps have been established asks for Aces and responder bids up the line to show how many they have. A further 5NT asks for Kings. 

After Stayman, Blackwood is probably the second convention most bridge beginners ever learn. It’s well-known but rarely played, having been supplanted by other slam-bidding methods, including its successor Roman Key Card Blackwood, which asks for ‘Key Cards’ including the King of Trumps. 

However, it is still a good place to start if you want to learn slam bidding and start getting those small and grand slam contracts.

Let’s find out a bit more…

Simple Blackwood Bids and Responses

The responses are extremely simple. A 4NT bid after trumps are agreed asks responder to show how many Aces he has. In the original Blackwood, aces are the only key cards shown, but other versions expand this to include the trump king and even the trump queen.

Response to 4NT Meaning
5 0 or 4 Aces
5 1 Ace
5 2 Aces
5 3 Aces

Here’s the convention in action:

Bidding After Blackwood

After asking for aces with the 4NT bid, the bidder has three obvious options:

  • Sign-off either at the 5-level or in a slam
  • Bid at the 5-level in an unbid suit, asking partner to bid 5NT (with the intention of passing)
  • Bid 5NT to ask for kings

The responses to the 5NT bid are:

Response to 5NT Meaning
6 0 or 4 Kings
6 1 King
6 2 Kings
6 3 Kings

Because the 5NT bid is a try for a Grand Slam, many partnerships have an agreement that they will not bid it unless all four Aces are held by the partnership.

A word of caution: a bit like Stayman, Blackwood suffers from the problem that it is almost too easy to learn. Players can learn the responses in a matter of minutes – and it often stops there. This results in them using Blackwood on hands where it is neither suitable nor sensible!

When Should You Use Blackwood?

The main reason to use Blackwood is to increase the accuracy of your slam bidding. For most players, its most useful feature will be in helping them avoid bidding small and gran slam contracts that won’t make.

The generally agreed prerequisites for bidding Blackwood are:

  • Trump suit has been agreed
  • You are interested in exploring the possibility of slam
  • You have no useless doubletons or void suit (see next section)
  • Partner's last bid was in a suit (not NT)

If these conditions have been met either player can bid Blackwood, although normally it is better for the stronger hand to do so since they will have a better idea of what you need for playing a small or grand slam. Depending on the circumstances, the stronger hand might be defined by either high card points (HCP) or length.

Of course, many players would point out that unless you are a beginner player you shouldn’t be playing Blackwood, and should instead learn Roman Key Card Blackwood or other slam bidding methods. We’ll take a quick look at the alternatives towards the end of this article.

Four Common Blackwood Mistakes

For most beginners the biggest mistakes when using Blackwood will come from using it when you shouldn’t. Unless you’ve got a bridge teacher looking over your shoulder or a partner who knows better, these mistakes can continue unchecked for a long time.

Mistake #1: Confusing Blackwood With Quantitative 4NT

The other main use of 4NT is as a quantitative bid asking partner to pass or bid 6NT, and there are a few circumstances where it may be easy to get the two confused.

Here’s an example:

Mistake #2: Using Blackwood for No Trumps Contracts

If you’re looking to explore a NT slam, Blackwood is not your friend. It forces the bidding too high, too quickly, and you should keep the 4NT as quantitative (see above).

Instead, use Gerber. By using 4 as the Ace-ask, the bidding is kept at a lower level. This also means you get to ask for Kings more often, which is important because you’ll need them if you’re not relying on shape to get you those 12 or 13 tricks.

Knowing when to use Gerber and when to use Blackwood takes some work between a partnership as there are a lot of different sequences that you may need to discuss. I started by assuming that any auction where opener bids or rebids NT used Gerber and went from there.

Mistake #3: Bidding Blackwood With a Useless Doubleton or Void Suit

You should only use Blackwood when you make use of partner’s response. Some hands, normally those with a useless doubleton or void, make this very difficult.

Take a look at the following hand for an example:

Mistake #4: Bidding Blackwood When You Can’t Deal With Every Response

You probably won’t make this mistake more than a few times because you feel pretty silly when you do it. Picture the scene: Clubs agreed as Trumps and you think there’s a possibility for a slam. Do you bid Blackwood? Sure!

Oh wait… partner bids 5 showing just one Ace and you realize a Small Slam is impossible – you really expected partner to show 2 or 3. Perhaps you’d better settle in game. The problem is… you’ve already gone past 5! Now you’ve only got two options, you can either bid 5 or 5, asking partner to bid 5NT (intending to pass) or you can bid the 6. Both could be problematic.

This can be solved pretty easily by stopping and running through partner’s possible responses and what they mean for your next bid.

Competitive Bidding

The unbalanced hand shapes that enable many trump slams are often mirrored in the hand shapes of your opponents, which means you might face competition, even at the 5-level.

There are several conventions used to deal with this including DOPI and DEPO.

Blackwood and DOPI

The most popular is probably DOPI (Double = 0, Pass = 1), which uses the following steps to show your hand:

Bid Meaning
Double 0 Aces
Pass 1 Ace
Cheapest Bid 2 Aces
Second Cheapest Bid 3 Aces
Third Cheapest Bid 4 Aces

Here’s an example of this in action:

Partnership Discussion Points

For such a simple convention, there are a surprisingly large number of ways to get it wrong. There are many different sequences you’ll need to discuss and it will depend upon the system and other conventions you are using. A good starting point is to discuss the following:

  • Which Blackwood? There's more than one type, so check you're both using the same convention!
  • Which common sequences lead to Gerber and which to Blackwood?
  • What convention will you use if your opponents interfere?
  • Do you ever use 5NT to ask for kings when you are missing an ace?

Blackwood Alternatives

Most players now use a form of Roman Keycard Blackwood instead of vanilla Blackwood. This convention counts “key cards” rather than Aces, enabling bidders to discover to check on the trump King and sometimes the trump Queen.

Sometimes asking for cards is the wrong approach, and players should also learn cue-bidding.


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