Artificial indicating that responder has no appropriate alternate bid, remains interested in the potential for a game contract and asks opener to bid again to show additional features.

There are two options to choose from:

• Fourth suit - forcing for one round;

•  Fourth suit game force - forcing to game.

Fourth suit should only be used when responder does not have another attractive bid available, such as:

• rebidding a 6-card suit;

• bidding no-trumps with a stopper in the fourth suit;

• raising partner's second suit with 4+ card support.

Opener responds to the fourth suit forcing by (in prioritised order):

• • raising responder's first bid suit with 3-card support;

  • bidding notrump with values in the fourth suit;

  • raising the fourth suit with four cards in that suit;

  • making the most natural rebid possible, lacking any of the above.

Using the "Fourth suit" convention may change the meaning of other bids, for example:

W N E S      

        P 1♣ P

1♥ P 1♠ P

3♥ - 5+♥, 13+ HCP if no fourth suit;

3♥ - 6+♥, 10+ HCP if fourth suit is using.