(Acronym for Double - 0, Pass - 1) [after RKCB it has altered to: Double = 0-3, Pass = 1-4, next step = 2 without the trump Queen, second step = 2 with the trump Queen].
It is used when an opponent overalls after partner biids 4NT (or 4♣) asking for Aces (but only when the overcall is below 5 of the trump suit):
Responses to 4NT (RCKB) when opponent interferes:
- Double= 0 or 3
- Pass= 1 or 4
- Next step = 2 without the trump Queen
- Second step = 2 with the trump Queen
