Quick summary

There are 5 key cards. A & K of trumps are equally important.

Only use if suit agreed, & you know what you'll do with the answer.

Avoid Blackwood if

Slam is off if:

  1. 2 Key cards missing
  2. Any missing (Grand Slam)

5NT is only to find out which King for GS

4NT is not always Blackwood

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Bridge Venue

Example Deal
+West
North
S 3
H K 8 5 4
D A K J 10 9 6
C K 5
+East
+South
Example Deal
Dealer: East
Vuln: All


Sorry partner, we should have been in a slam.
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Slam bidding. Blackwood

Hey partner, Suit Slam on! How many Aces have you got?

The "Blackwood" (1) convention is a way of asking your partner how many Aces or Key cards they hold, after the suit has been agreed between you. (If you want to ask about Aces in a NT contract, use Gerber, and bid 4club).

In a suit Slam, your opponents will generally play their aces straight away, so if you lack any of them, or don't have a void in that suit, there's a good chance you'll lose the corresponding trick. Since you can only afford to lose one, or none at all in a Grand Slam, this is pretty important stuff.

Actually, in a Slam, the King of trumps is just as important as the Ace of trumps. So there are 5 Key cards, namely the 4 Aces plus the King of trumps.The original version of Blackwood only asked for Aces, but that has been superceded by a system which asks about all 5. It's called "Keycard Blackwood" and there are two versions

All 3 systems use 4NT to ask partner how many of the cards they hold. KCB is almost identical in use to the original Blackwood; only the 5diamond response is different. The 5diamond response used to mean "I've got one". Now, with KCB, it means "I've got either one or five" (one and five are unlikely to be confused in practice!!). Here are the replies:

  • 5club=0 or 4 key cards
  • 5diamond=1 or 5
  • 5heart=2
  • 5spade=3

The "Roman" version is a little more complicated, and gives data on the queen of trumps.

Don't raise to slam if you are missing 2 key cards

If you are missing two key cards it's likely you are going to lose tricks ! Of course you might have a void to help you (a void is another way to 'control' a suit), but usually you won't know if it's in the right suit, especially if 2 key cards are missing. To know this, you need to be using Splinters or Cue bidding. Remember, unlike Cue bidding, Blackwood does not ask about 'controls', but about key cards.

Grand Slam ? Bid 5NT only if you have all 5 key cards

If and only if the answer is "I've got all 5" should you consider a question about Kings by bidding 5NT, with a view to going to Grand slam at the 7 level. You will have decided that a Small slam is OK, and so that if the wrong answer comes back at the 6 level, you will be happy to play a small slam. If you are not considering a Grand Slam, why ask the question ? Just put it into a small slam in the agreed suit.

Don't use Blackwood if:

  • you are trying for a No Trump slam: (UseQuantitative bidding)
  • you have Weak suits:  Suits with 2 or more cards must have an Ace or King. Otherwise you might mean lose 2 tricks straight off. (Use Cue bidding because you need to know if you have a void opposite any weak suit, and you need to know where the controls are, i.e. in which suit. You can also use the Losing Trick Count to help your thoughts).
  • you have Void suits:  You don't know which suit is void, and you don't know which Aces you don't have.  (So use Cue bidding).
  • If the response might go too high:  For instance, if club are agreed as trumps, and you need 2 key cards from partner for slam, then a 5diamond reply showing only 1 key card is a disaster. You are forced to bid 6club. In other words, you need to hold 3 key cards yourself to use Blackwood if the agreed suit is club, or 2 of them if it's diamond. (The alternatives are Cue bidding and the Losing Trick Count).

(1) Named after Mr. Easley Blackwood, a bridge pioneer.

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