|5||0 or 4 aces|
All of the rebids made by the Blackwood bidder are natural, with the exception of 5NT. If the Blackwood bidder is contemplating a grand slam and needs to know how many kings his partner has, he can rebid 5NT. The responses to 5NT are:
|6||0 or 4 kings|
There are a number of ways to show aces if 4NT is overcalled. One method is DOPI, which stands for "Double = Zero aces, Pass = 1." The cheapest available bid shows two aces, the second-cheapest bid shows three aces, and the third-cheapest bid shows four. Another method of showing aces is DEPO, which stands for "Double = Even number of aces, Pass = Odd number of aces."
Note that on occasion the responder to a Blackwood inquiry will have a void somewhere in his hand. Voids should not be treated as aces; how they are treated instead is up to partnership agreement.
Blackwood gets its name from its inventor Easley Blackwood, the late American player and writer.
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