Fourth Suit Forcing
The most common use of Fourth Suit Forcing is when responder has game-going values (12+ HCP) but no stopper in the unbid suit for No Trump, no fit yet for either of opener's suits, and a hand not suited to rebidding their own suit. In the auction 1♣ - 1♥ - 1♠, a bid of 2♦ by responder is Fourth Suit Forcing.
Opener must not pass. Opener's priorities when replying to the fourth suit are tabled below - agree with your partner whether FSF is forcing to game or forcing for one round only.
| Auction so far | Opener's Reply |
What opener's reply means |
| 1♣ - 1♥ - 1♠ - 2♦ | 2 NT | A stopper in the fourth suit (Diamonds) - suggests No Trump |
| 1♣ - 1♥ - 1♠ - 2♦ | 2♥ | 3-card support for responder's first suit (Hearts) |
| 1♣ - 1♥ - 1♠ - 2♦ | 3♣ | Extra length (6+ cards) in opener's first suit, no Diamond stopper |
| 1♣ - 1♥ - 1♠ - 2♦ | 2♠ | 5 Clubs and 4 Spades (extra shape), no Diamond stopper |
| 1♣ - 1♥ - 1♠ - 2♦ | 3♦ | 4 cards in the fourth suit (rare) - raises the "phantom" suit |
Table of opener's replies to a Fourth Suit Forcing bid
Practice your Fourth Suit Forcing Bids
Match the reply to its meaning
Partner opens 1C, you respond 1H, partner rebids 1S
With this hand you have 16 HCP - easily enough for game - but which game?
- ♠ A 3
- ♥ K Q J 8 5
- ♦ 7 4 2
- ♣ A Q 4
You cannot bid No Trump with three small Diamonds, and you have no fit yet for partner's suits. Bid 2♦ - Fourth Suit Forcing. If partner bids 2NT (Diamond stopper) you raise to 3NT; if partner shows 3-card Heart support you head for 4♥.