4th Suit Forcing

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On the auction below which hand does North have for their jump to 3♠? If 3♠ shows hand 1, what should North bid with hand 2 which has invitational values? If 3♠ is invitational, what should North bid with the game forcing values of hand 1?

On the auction above, South has a wide range 12-17 points. So North must strive to keep the auction open if a game may be available. Even if North is weak and a game isn’t available, North may have a preference for another suit. So a 2♠ rebid doesn’t show invitational values, it simply shows 5+ spades and a desire to improve the contract. To show invitational values with 5+ spades, North jumps to 3♠ (hand 2).  

North shouldn’t jump to 4♠ with hand 1 for several reasons:

1. North doesn’t know whether South has 3-card spade support. Another strain may be better.

2. Even if South has 3-card spade support, a jump to 4♠ consumes bidding space needed to assess whether a slam is available.

Responder has plenty of invitational bids available.  On the above auction below, responder can bid a natural 2NT, 3♣, 3♦, or 3♠ to invite game.  When responder has a game forcing hand, they need an easy reliable way to establish a game force.  

 
4^th Suit Force provides an easy way to establish a game force, look for the right strain, and assess whether a slam is available. After 3 suits haven been bid without a jump, responder’s bid of the 4^th suit is artificial and game forcing. Bidding proceeds naturally. Playing 4^th Suit Forcing, North’s rebids 2♥ with hand 1.  North’s 2♥ bid is artificial and game forcing.

Continuations after 4^th Suit Forcing

Opener rebids naturally after responder's 4^th Suit Forcing artificial game force.  Opener's options include:

• Showing a stopper in the 4th suit by bidding notrump
  With just the Ace, a non-positional stopper, opener may prefer giving responding the chance to declarer a notrump contract to protect a positional honor.
• Showing 3-card support for opener's suit
• Bidding the 4th suit at the 3-level to show 4 cards in the suit
• Rebidding a suit to show extra length

Sometimes opener's hand will not fit any of the available bids.  Read our Punt Bids article to learn what opener should do when no good bid is available.  

The auction continues naturally, looking for the right game.  When choosing which game to play, you will generally want to follow the priorities below.

1. Choose a major suit game with an 8+ card fit.
2. Otherwise, choose 3NT if feasible.
3. If not feasible, consider playing in 4♥ or 4♠ in a 7-card fit.
4. If not feasible, fallback to game in a minor.

5♣ and 5♦ are the games of last resort because they require 11 tricks and pay only 20 points per trick.  

When 4^th Suit Forcing Applies

4^th Suit Forcing is off when the opponents bid a suit. Use a cue bid of the opponent’s suit to force. 4^th Suit Forcing is off after a jump bid. 4^th Suit Forcing doesn’t apply in a 2/1 Game Force auction. A bid of the 4^th suit is typically natural or a notrump probe. A bid of the 4^th Suit by a passed hand is natural and non-forcing. If you play XYZ, 4^th Suit Forcing doesn’t apply when 3 suits have been bid at the 1-level. XYZ takes precedence.

When an uncontested auction begins 1♣ - 1♦ - 1♥, it is common to play a 1♠ rebid by responder as natural and forcing, but not forcing to game. Many partnerships use a jump to 2♠ as 4^th Suit Forcing, an artificial game force. That is our recommendation, but it requires discussion with your partner.

Jumps in the 4^th Suit

We recommend using jump in the 4^th suit as natural and invitational showing at least 5-5 distribution.  

On the above auction, North is showing North is showing a good 5-5 invitational hand (e.g. ♠KQ752 ♥AJ962 ♦84 ♣7).

Simlarly, a 4^th suit jump in a minor suit is also a natural and invitational with at least 5-5 distribution.  

There is one auction where the 4^th suit can be bid at the one level.  The meaning of a 4^th Suit Jump in spades depends on whether you use 1♠ or 2♠ as 4^th Suit Forcing.

Our recommendation for advanced partnerships is to play XYZ when 3 suits have been bid at the 1-level.  If your partnership doesn't play XYZ, we recommend using a jump to 2♠ as 4^th Suit Forcing,  With that agreement, North's jump to 2♠ in the above auction is an artificial game force.  The 4^th Suit Forcing jump to 2♠ doesn't deny holding 4 spades, opener should bid 3♠ if they have 4 spades.  

A 1♠ rebid by responder is natural and forcing for one-round, making it easy to find 4-4 spade fits.  

Please discuss this topic with your partner to make sure you have a firm agreement.