Splinters, CRO, UCB

A double jump response in a new suit is called a splinter. 1H - PASS - 4C

A splinter bid shows four card support in Opener’s suit and first round control in the new suit ie. an Ace or a void. 

The responders hand should have at least 10 points since a game level contract is the minimum rebid. 

Any bid of a new suit after the splinter is a cue bid showing an interest in a slam. 

Michael’ is an Overcall that is used to show a two suited hand.

CRO is like Michaels - a system for bidding 2 suited hands. These are immediate bids over an Opposition 1 level bid.

The cue bid C is for Colour 

1C - 2C or 1S - 2S, shows 5+ H, 5+ D

A 2NT bid is for Rank

1C - 2NT or 1D - 2NT shows 5+ H, 5+ S

A 3 Club bid is for Other. There will always be a major, and a minor

1C - 3C shows 5+ S (Major in the same colour) H, 5+ D (the other Minor)

1D - 3C shows 5+ H (Major in the same colour) H, 5+ C (the other Minor)

1H - 3C shows 5+ D (Minor in the same colour) H, 5+ S (the other Major)

1S - 3C shows 5+ C (Minor in the same colour) H, 5+ H (the other Major)

Unusual NT is a Cue Bid that is similar to Michael’s. It is an Overcall that shows the two lowest unbid suits.

If you use an UCB after Partner’s Overcall, you are promising at least ​3 cards in Partner’s suit ​and​ 10+ points. 

The bid is not game forcing so the Opener can rebid her opening suit depending the strength.

eg. 1C - 1S - PASS - 2C (“I have at least 3 Spades and 10+ points”). 

Remember that a game in a Minor requires 27+ points, therefore the UCB work better in major suits.