42 (or Texas 42) is a game played with a standard set of 28 "Double-Six" Dominos, that is similar to "Trick-taking" card games.
Four players in two partnerships are each dealt 7 dominoes. Players then bid for the right to declare trump. The bid goes around once, with bids ranging from 30 to 42, plus some special bids. The winning bidder declares a trump. The object is to win "tricks."
The highest domino of each suit is the double. Play is then started by the winning bidder by placing a domino to start a trick. Players must follow suit if possible. The higher end of the domino led determines the suit for that round. If a player cannot follow suit, they can play any domino. The trick is won by the highest trump in the trick, or if it contains no trump, by the highest domino of the suit led. The winner of a trick leads to the next.
Scoring for a round is one point per trick (7 tricks) plus the "count". The "count" is determined by dominoes taken that add up to 5 (0-5, 1-4, 2-3) or 10 (6-4, 5-5). They are worth 5 or ten points respectively, giving a total maximum score of 42, and the name of the game.
A match is seven hands, or marks. Traditionally, scoring is the seven marks required to write the letters ALL.