After opener makes his rebid, the Impossible Negative bidder has two types of rebids to disclose his shape and values, as follows.
Responder can make a jump rebid in his singleton suit, assuming opener has not bid the suit naturally. For example:
|1NT||:||Showing 4-4-4-1 shape and 8+ points. (Club singleton.)|
If opener has bid responder's singleton suit, responder can jump in notrumps. For example:
|1||:||2NT!||Showing 4-1-4-4 shape and 8+ points. (Heart singleton.)|
|:||2NT!||Showing 1-4-4-4 shape and 8+ points. (Spade singleton.)|
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