Exclusion Blackwood: Key Card Asks With a Void

Exclusion Blackwood is a jump to the five level in a new suit, after a trump suit is agreed, that shows a void in that suit and asks partner for key cards outside it. Partner counts the aces and the trump king but ignores the ace of the void suit, which would be wasted, and answers in steps.

It is also called Voidwood or Exclusion Key Card Blackwood. It is an expert add-on to Roman Key Card Blackwood in 2/1 Game Force, Standard American and Acol partnerships, and it fixes the one hand type that ordinary 4NT handles badly: the hand with a void.

With a void, ordinary Blackwood fails for a simple reason. If partner shows one key card, you cannot tell whether it is a useful ace or the ace of your void suit, where it takes no trick at all (you would ruff that suit anyway). You end up guessing, or stopping at the five level when slam is cold.

Exclusion Blackwood removes the guess. The bid itself names the void:

1. A trump suit has been agreed, either directly or by clear inference.
2. You make an unusual jump to the five level in a new suit. For example, 1♠ - 3♠ - 5♦. You could not want to play in diamonds at the five level after agreeing spades, so the bid is artificial: "I am void in diamonds. How many key cards do you hold outside diamonds?"
3. Partner counts the other three aces and the trump king, four key cards at most, and answers in steps.

The answers use the same order as your normal RKCB. With 1430, that means:

Pairs who play 3014 swap the first two steps. A few pairs play a simple count instead (0, 1, 2 and so on), arguing that partner of an exclusion bidder rarely has three or four key cards. Pick one order and use it for both 4NT and Exclusion, so there is less to remember.

The steps start from the bid directly above the exclusion bid. In a major-suit auction, the possible exclusion bids and their four steps are:

Spades agreed

Hearts agreed

Every answer in a major-suit auction stays at or below six of the trump suit, so you can always stop in the small slam. With a minor as trumps that is no longer true: after a 5♠ exclusion bid with clubs agreed, some answers are above 6♣. Use Exclusion with a minor only when you can stand every answer.

Once you know the key cards, you place the contract:

• Two or more key cards missing (outside your void): sign off at the cheapest level of trumps. If partner's answer was itself the trump suit at the five level, you can pass.
• One key card missing: bid the small slam when your side holds the trump queen (or a ten-card fit). If the queen is also missing in an eight-card or nine-card fit, two trump honors are out, so sign off.
• None missing: look for the grand, with the trump queen held.

The queen ask. After a 1st-step or 2nd-step answer, the trump queen is still unknown. As in RKCB, the cheapest bid that is not the trump suit asks for it. Partner signs off in trumps without the queen and bids on with it. Many pairs simply skip this with a ten-card fit.

Kings. Some partnerships use the next free bid after the queen answer as a king ask. In practice most grand slams after an exclusion bid are bid on key cards, the queen and a count of tricks. If you need a specific king, you probably should have cue bid first.

Both deals start the same way. You are South and open 1♠ with a seven-card or six-card spade suit and a diamond void. Partner gives a limit raise to 3♠ (10-12 points, four trumps). Now you know the fit, and your diamond void makes your hand much stronger. The question is which aces partner holds.

You hold ♠KQJ975, ♥AQJ4, ♦void, ♣K86: 16 HCP. Your key cards are the ♠K and the ♥A. Outside diamonds, the missing key cards are the ♠A and the ♣A.

If you bid 4NT, partner answers 5♣ (one key card in 1430). That card could be the ♠A or the ♣A, and then slam is good. But it could also be the ♦A, and then both the ♠A and the ♣A are missing. You cannot tell, so you must stop at 5♠.

With Exclusion, you bid 5♦. Partner ignores the ♦A and shows one key card outside diamonds with 5♥, the first step. Exactly one of the ♠A and ♣A is missing, so you bid 6♠.

Partner's key card is the ♠A. Declarer loses the ♣A and nothing else: six trump tricks, four hearts, one club trick after the ace (the ♣K and ♣Q take only one trick between them) and a club ruff in dummy. Note that partner's ♦Q and ♦J are wasted opposite the void, which is why counting HCP alone would have misled you.

Now you hold ♠KQJ9753, ♥AKQJ, ♦void, ♣A2: 20 HCP and a self-sufficient hand. You have three of the four key cards outside diamonds. Only the ♠A is missing, and partner's limit raise may or may not include it.

Count your tricks if partner has the ♠A: seven spades, four hearts, the ♣A and a club ruff in dummy. That is thirteen. So the grand slam depends on one card. You bid 5♦, and partner's 5♥ shows one key card outside diamonds. It must be the ♠A, since you hold the other three. You bid 7♠.

With ordinary 4NT, partner's 5♣ answer could have been the ♦A, and you would have had to settle for six. Exclusion turned a guess into a certainty.

1. Counting the ace of the void suit. Partner must leave it out. That is the whole idea.
2. Using it without an agreed trump suit. A jump to five of a new suit with no fit is natural or a misunderstanding. Agree that Exclusion applies only after a fit is clear.
3. Confusing it with a splinter. A double jump to the three or four level (1♠ - 4♦) is a splinter, showing shortness and a raise. Exclusion is a jump to the five level.
4. Using it with a singleton. Exclusion promises a void. With a singleton, partner's ace in that suit is still useful, so plain RKCB is right.
5. Going past six of a minor. With clubs or diamonds as trumps, some answers can be too high. Check before you bid.
6. Bidding Exclusion with two fast losers in another suit. Key cards do not cover a holding like two small. Cue bid first.

For 3014 players, the 1st and 2nd steps are reversed.

Before you agree on Exclusion with a new partner, see what 5♦ means in every system after 1♠ - 3♠, so you know how the robots read the jump. Void hands are rare enough that most players never get a feel for them. The BridgeDummy Bidding Room helps here because every deal is a fresh random hand bid with EPBot robots, and you see the full layout after each board. When you want to measure how often a slam with a void really makes, a custom simulation lets you set both hand types and compare 5♠, 6♠ and 7♠ over many dealt hands.

• Roman Key Card Blackwood: the 4NT ask that Exclusion is built on.
• Splinter bids: showing shortness below game.
• Slam bidding: the full set of slam tools.
• Blackwood convention: the original ace ask.