Source: Bridge Guys
This conventional variation of the Six Ace Blackwood convention was devised by Mr. Edwin Kantar, and published in his book Roman Keycard Blackwood.
In one or several of these publications Mr. Edwin Kantar addresses the conventional method designated as Six Ace Blackwood, which he has varied and modified to meet the same requirements in a revised manner, but which continues to have similarities to the Six-Ace Blackwood conventional method known as 6A-RKCB, the origin of which is unknown.
The concept behind this variation is the same, namely first to discover that the partnership possesses two suits of eight cards or more (so-called double suit agreement), so that there are two combined suits and therefore two suit fits. Once this feature has been discovered, then either partner of the partnership can initiate the artificial 4 No Trump bid to determine whether or not slam is a possibility.
The partnership attempts to discover the number of Aces, which are considered Key Cards, and also whether the partnership possesses both Kings of the two suits, also known as Key Cards. The official designation of Six Ace Keycard is somewhat a misnomer, or a name wrongly or unsuitably applied, since Kings are not Aces.
As soon as the partnership has established the trump suit or inferred the trump suit, then one partner will initiate the 4 No Trump bid to ask for Aces and Kings. The responses of the partner are shown below and these responses are the responses suggested by Mr. Edwin Kantar in his publication(s).
5: Shows 1 or 4 Keycards. In this response no information about either Queen of the two suit fits is included. 5: Shows 0 or 3 Keycards. In this response no information about either Queen of the two suit fits is included. 5: Shows 2 Keycards. This response also shows that the partner holds no Queen in the two suit fits. 5: Shows 2 Keycards and possession of the lower-ranking Queen of the two suit fits. 5NT: Shows 2 Keycards and possession of the higher-ranking Queen of the two suit fits. 6: Promises both Queens of the two suit fits.
According to the modifications of Mr. Edwin Kantar there is not any possibility to show a void such as a distribution of 6-4-3-0. This is owing to a lack of bidding space. This is also the case with the version known as Six Ace Roman Keycard Blackwood or, as it is more commonly known, Six Ace Blackwood.
Following the two responses of 5 Clubs and 5 Diamonds there might be instances, in which it would be preferable to know whether or not there are no Queens, 1 Queen, or even both Queens are held in the agreed two suits. Mr. Edwin Kantar suggests the following guidelines to discover whether or not any Queen is held in the two suit fits.
If the response is 5 Clubs, then 5 Diamonds is the Queen-asking bid.
5: Shows an absence of both Queens. 5: Promises the Queen of the lower-ranking suit of the two suit fits. 5NT: Promises the Queen of the higher-ranking suit of the two suit fits. 6: Promises both Queen of the two suit fits.
If Diamonds is one of the agreed two suits, then the next higher-ranking suit, which is not one of the agreed two suits, becomes the Queen-asking bid. In this instance the steps will simply be identical in significance although different in rank.
If the response is 5 Diamonds, then the Queen-asking partner employs the following guidelines:
5: This is the correct bid if Hearts is not one of the agreed two suits. If Hearts is one of the agreed two suits, then Spades becomes the Queen-asking bid and the ensuing steps according to the guidelines show an absence or possession of the Queen(s) of the agreed two suits. If Spades is the second agreed suit, then 5 No Trump becomes the Queen-asking bid, and the steps are adjusted accordingly. This particular bidding sequence, however, requires that the partnership hold the values to safely play a small slam contract. (If these values are not present, then the partnership should agree to a sign-off bid.) 5: This is the correct bid if Spades is not one of the agreed two suits. 6: This is the correct bid if Spades and Hearts (both Major suits) are the agreed two suits.
Once the Queen-asking bid has been initiated, then the answering partner responds in steps according to the following guidelines:
First Step: Shows the absence of any Queen of the agreed two suits. Second Step: Shows the lower-ranking Queen of the agreed two suits. Third Step: Shows the higher-ranking Queen of the agreed two suits. Fourth Step: Shows both Queens in the agreed two suits.