Fourth Suit Forcing (to game)

When responder is an unpassed hand and rebids the fourth suit in an uncontested auction, his bid is artificial, shows 12+ points, and is game-forcing.

For example,

1 - 1 - 2 - 2

2 is artificial and a game-force. Opener's rebids, in order of priority, are:

• 2 of responder's major - 3-card support
• Any rebid of opener's suits - Natural, waiting
• Raise of the fourth suit - Tends to show 4-card support, waiting
• 2NT - Natural, with a stopper in the fourth suit

FSF does NOT apply in the following situations:

• 1 - 1 - 1 - 1. While 1 is forcing, it is not a game-force. (Unless you play Walsh.)
• When responder's first bid is at the two-level, a fourth suit rebid is not artificial, since a game-forcing situation has already been created.
• When responder jump rebids the fourth suit. The jump rebid shows invitational values and at least 5-5 .
• In competition.

From Connie DeLisle:

I like the Aces Scientific view of 4th suit forcing. The priorities are:

• NT with stopper unless 5-5 or better
• support with 3 cards
• raise the 4th suit with 4
• return to your original suit with none of the above

The reason 1 and 2 should be interchanged is that the 4th suit forcing bidder can bid his suit a second time to show 5. It may be too late otherwise to know if a stopper is in opener's hand for NT.