Two popular conventions are the Michaels cue Bid and the Unusual No Trump. The latter is often referred to as the Unusual 2NT, but the same principles often apply whenever a no trump bid cannot be natural.
A direct cue bid of a minor opening bid shows both majors, at least 5-5 shape. The cue-bid of a major opening shows the unbid major plus either minor suit, at least 5-5 shape.
Non-vulnerable a Michaels Cue Bid can be made on any strength of hand – a weak hand will not bid again, a strong hand will make a strength-showing call.
Vulnerable a Michaels Cue Bid should be a reasonable hand or better, that is, not extremely weak. A hand with 5 or 6 losers would be the minimum.
Responder assumes that partner has the weaker hand and bids accordingly. A strong hand can RELAY with 2NT, asking the overcaller to show their hand type and strength.
When the cue bid shows the unbid major and unknown minor, advancer can bid a minor as pass or correct: that is, if you have the minor then you pass, otherwise you bid on. This implies strength in the minor if you are forcing to a higher level.
For example:
(1H) 2H (Pass) ? S x H xxxx D xxxx C xxxx Partner has shown 5 spades and a 5-card minor. Bid 3C, asking partner to pass if they hold clubs or bid diamonds if they have 5 diamonds. You are happy to play in either minor rather than spades. | (1S) 2S (Pass) ? S xxxx H A With a big club fit, bid 3D to play if partner has diamonds but you are prepared to play higher if they have 5 clubs. |
(1H) 2H (Pass) ? S Axxxxx H xxxx D x C xx Bid 4S. This is a double shot: you hope to make, albeit unlikely, or it may be a good sacrifice. | (1D) 2D (Pass) S Axx 3C Good hand, hearts equal or longer 3D Good hand, spades longer 3H minimum, 5-5 3S does not exist |
(1H) 2H (Pass) ? S Axx H xxx D KJxx C Ax Bid 2NT. You intend to bid game if partner shows a good hand or a hand with diamonds. The responses to 2NT are: 3C 5 clubs, minimum 3D 5 diamonds, minimum 3H 5 clubs, non-minimum 3S 5 diamonds, non-minimum |
A direct jump overcall of 2NT shows a hand with at least 5-5 shape in the two lower unbid suits.
Non-vulnerable the UNT can be made on any strength of hand – a weak hand will not bid again, a strong hand will make a strength-showing bid.
Vulnerable the UNT should be a reasonable hand or better, that is, not extremely weak. A hand with 5 or 6 losers would be the minimum.