Fourth suit forcing is a convention. This convention is alertable.
In non-competitive auctions, it often happens that three suits are bid and no fit is found, as in
| Opener | Responder |
|---|---|
| 1♣ | 1♥ |
| 1♠ |
The opener's 1♠ bid was forcing. Responder now has several options:
- With a minimum, responder can rebid one of the previously mentioned suits or notrump at the cheapest level.
- With any more, the responder must either make a jump rebid of a previous suit or notrump, or bid 2♦.
Since a diamond fit is unlikely, and since the jump bids don't make a distinction between invitational and game-forcing strength, the fourth suit forcing convention was developed.
There are a number of different ways to treat this convention:
- The fourth suit bid may be invitational, in which case the jump is game-forcing.
- The fourth suit bid may be game-forcing, in which case the jump is invitational.
- The fourth suit is invitational at the two-level and game-forcing at the three-level.
In all cases, the fourth suit is forcing and artificial.
An alternate name of this convention is fourth suit artificial since the emphasis of this convention is that the fourth suit bid is artificial.
One possible treatment: fourth suit bid invitational
Convention
A fourth suit bid by responder following a one-over-one response, shows invitational strength, is artificial, and forcing one round.
Exception
1♠ may be bid as a fourth suit (i.e. 1♣-1♦-1♥-1♠) with less strength.
Opener's next bid
With a minimum, opener should describe his hand by either
- bidding any of the three previous suits at the cheapest level.
- this requires 3 trump in partner's first suit or extra length in one of his own suits
- bidding the fourth suit to show four. This does not establish a fit.
- bidding 2NT, suggesting but not requiring a stopper in the fourth suit (this is a catch-all if no other bid applies).
Occasionally the fourth suit bid will be 3♣. In this case, the 2NT catch-all is no longer available, so 3♦ may be used as a waiting bid and then no longer promises extra length or fit.
With extra strength, opener bids 3NT (requires a stopper in the fourth suit) or jumps the bidding (never exceeding 3NT). If the jump bid would exceed 3NT, then the bid must be made without jumping. Any bid above 2NT is therefore forcing, since opener may not have had space to show extra strength.
Responder's third bid
Minimum bids are natural and invitational if below game. Jump bids are natural and forcing if below game.
In competition
The convention is off in a competitive auction. Any fourth suit bid must be real.
External links
- http://bridgehands.com/F/Fourth_Suit_Forcing.htm (a different treatment)