Source: Wikipedia

Texas transfer, or simply Texas, is a bidding convention in contract bridge. Originated independently by David Carter of St. Louis and Olle Willner of Sweden, and used in response to a notrump opening when holding a six-card or longer major suit, game-going points and no interest in slam, its objective is to make the notrump opener the declarer in a game contract in the major suit.

After a notrump opening, responder bids the suit below his major at the four-level, i.e. if he holds hearts, he bids 4and if he holds spades, he bids 4. Opener is obliged to bid the next available major suit, i.e. after a 4 bid by responder, he bids 4and after a 4response, he bids 4setting the contract.

In the variant known as South African Texas, responses of 4and 4are used as transfers to hearts and spades respectively.

The standard defense to the Texas Transfer: double is one-suited and lead-directing, 4NT is for the minors, four of responder’s suit is a Michaels cuebid. A delayed double after opener accepts the transfer is a three-suited takeout.

Both Texas and South African Texas transfers may also be used as opening pre-emptive bids. A 4and 4can show a slightly different hand type (usually stronger) compared to a direct 4or 4opening.