Bidding and playing a slam (12 tricks) is quite rare but earns big bonus points.
If you and your partner have a very strong hand (33 points plus) or a fit of extraordinary quality then a slam should be explored.
By checking how many aces and kings you hold between both hands you can bid a slam with confidence.
The convention we use to count aces and kings is called ‘Blackwood’. A convention means the bid has a special meaning and is not natural.
To begin Blackwood - bid 4NT - which asks your partner to bid the number of aces she has. The bid of 4NT is never natural. Partner must respond.
The formula used to respond to 4NT is:
5C = nil or four aces
5D = one ace
5H = two aces
5S = three aces
After the reply has been given for Aces, a bid of 5NT can be used to ask for the number of kings.
The formula used to respond to 5NT is:
6C = nil or four kings
6D = one king
6H = two kings
6S = three kings
Bidding is completed by a contract of 6 or 7 in a suit or NT.
Slams in a suit can be obtained with a good fit. A slam in NT needs 33 points.
If, when using Blackwood you find you are missing too many aces then bid 5 of your agreed suit. Your partner must not bid after this.