Double Club System

Auctions starting 1C, 1H/S

What has been shown?

Opener has shown either an unbalanced hand with no suit longer than clubs or a balanced hand with 17+ hcp.

Responder has either a 5-card suit and 4+ hcp or a 4-card and 12+ hcp. Opener can assume a 5-card suit for now, since responder is strong enough to correct to no trumps if he has only a 4-card suit.

Continuations by Opener

1S (over 1H)
Natural and forcing. Shows a 4-card spade suit in addition to a 4-card or longer club suit. Opener's club suit will always be 5-card or longer unless he has a 4=1=4=4 shape. Further bidding is natural.
Note: This bid is forcing since it makes little sense for responder to pass it. If he has 4-card support for spades and a minimum hand then has can bid 2S. With any other minimum hand he can make a natural bid, such as 1NT, preference to clubs, or a repeat of his own suit. Since this bid is forcing there is no need for the jump to 2S to be natural, so it becomes a splinter in support of hearts.
1NT
Forcing. A balanced hand of 17-19 hcp or 25-28 hcp. Does not deny support for responder's major, nor does it deny a 4-card or 5-card holding in the other major.
Memory Guide: Opener's 1NT rebid is forcing since responder cannot have a hand where it is right to pass 1NT. If responder is weak then he has a 5-card suit and should remove to a part-score in the known 5-2 or better fit.
2C
Natural and non-forcing. Further bidding is natural.
2D
Artificial, showing a club hand of at least game-invitational values opposite a minimum response. Forcing to at least 3C. Responder should continue naturally, except that a light or minimum responder (4-7 hcp) must rebid his suit. (A stronger responder may also rebid his suit, if that is his natural bid, but since he knows that game values certainly exist he will continue with a further natural bid on the next round.)
2H (over 1S)
A natural and forcing reverse, showing 4+ hearts and longer clubs. Forcing to at least 3C.
2H/S (raise of suit)
Natural weak raise of responder's suit. May be only 3-card support, since responder will either have a 5-card suit or be strong enough to continue with 2NT.
2NT
A balanced hand of 20-22 hcp or 27-30 hcp. Does not deny support for responder's major, nor does it deny a 4-card or 5-card holding in the other major.
3C
Natural and non-forcing, but showing a strong hand and a good club suit. Further bidding is natural.
jump new suit [Alert]
Splinter, showing 4-card support for responder and shortage in the bid suit.
3H/S (raise of suit)
Natural invitational raise of responder's suit. May be only 3-card support, since responder will either have a 5-card suit or be strong enough to continue with 3NT.
3NT [Alert]
An artificial strong raise of responder's suit. Opener has 4-card or longer support and is very strong and semi-balanced (no splinter). Opener does not have a balanced hand since he would have rebid in NT, so responder can assume that opener has a 5-card club suit as well as exactly 4-card support for responder's suit, probably with two doubletons on the side, so he is well-positioned to assess the degree of fit between the two hands. Responder should make a slam try unless minimum or non-fitting. Responder's weakest action is to sign off in 4H/S.

Author: Chris Burton
Gravesend Bridge Club