Bridge

Roman Key Card Blackwood (1430)

Ask partner for key cards (aces + king of trumps) before slam.

sequence
... — 4NT — (5♣/5♦/5♥/5♠)
how it works

Modern Blackwood counts five key cards instead of four: the four aces plus the king of the agreed trump suit. In the 1430 variant, 4NT asks and responses are: 5♣ = 1 or 4 keycards, 5♦ = 0 or 3, 5♥ = 2 without the trump queen, 5♠ = 2 with the trump queen. The asker can then sign off in 5 of trump, bid 5NT to ask for kings (implicitly confirming all keycards are held), or leap directly to slam.

used in 934 places