in his hand. With no aces or four, partner replies 5; with one, two, or three aces, 5, 5, or 5, respectively. In a more modern form, known as Roman Key Card Blackwood (RKCB), the 4NT bid asks partner to disclose the number of key cards held where the five key cards are the four aces and the king of trumps. Responses are stepwise: 5 for 0 or 3 key cards, 5 for 1 or 4, 5 for 2 without the trump queen, 5 for 2 with the trump queen. Some prefer to reverse the meaning of the first two responses and the variants are referred to in abbreviation as RKCB 3014 and RKCB 1430 respectively. Various methods are used to continue with king-asking and queen-asking bids. Gerber This is similar to Blackwood but the ace-asking bid is 4 rather than 4NT. The responses are 4 for 0 or 4, 4 for 1, 4 for 2, and 4NT for 3. Similarly, a 5 bid following an ace-ask asks for kings. Gerber is a jump bid to 4 used after a notrump opening bid and on other occasions by partnership agreement. Culbertson 4–5 NT Culbertson 4–5 NT was the first slam bidding system to gain widespread approval; it was part of the Culbertson system through the 1930s, and was part of the British Acol system for many years. After suit agreement, the bid of 4NT showed two aces and the king of a (genuine) bid suit, or three aces. Responder would make one of these bids: five of the lowest bid genuine suit to deny an ace; bid a suit (if necessary at the six level) to show the ace of that suit. Bid 5NT to show two aces. There are various subtleties, and both partners are allowed some latitude for judgement. The convention is rarely used today. Quantitative notrump bids These are used to establish whether two relatively balanced hands have sufficient high card points (HCP) to make a slam or grand slam contract in notrump; used after a notrump opening bid. Cue bid Cue bids are a co-operative system. Cue bids are used to communicate specific controls (aces or voids, kings and singletons). Once a trump suit has been agreed and the two hands are considered to be strong enough, partners bid the lowest available suit which they control; this process continues until one of the partners has sufficient