The Blackwood convention
Blackwood is a slam-going convention: a bid of 4NT asks partner how many aces they hold.
When it is used
When the partnership has the points for slam, you check for aces before committing, so missing aces don’t cost you the contract. 4NT is Blackwood when you have agreed where to play.
Partner answers at the five level, and the suit gives the count: 5♣ shows 0 or 4 aces, 5♦ one, 5♥ two and 5♠ three. With two aces missing, sign off below slam; with one missing, bid the small slam.
An example
You raised partner’s spades to game. Partner now bids 4NT. You hold this hand.
- ♠ K 8 5 4
- ♥ A J 6
- ♦ 7 4 2
- ♣ A 8 3
Answer 5♥: you have two aces, the ace of hearts and the ace of clubs.
Where we teach it
Taught in the Beginner course, in the Slam Bidding topic, in both systems, ACOL and 5‑card majors. Improver revisits Blackwood and the other meanings of 4NT, and Roman Key Card Blackwood is an Advanced topic.
Learn it properly
Bridge Unlocked teaches the game step by step, with real hands to play. Bridge Basics is free.