Dominoes are rectangular tiles graded with all possible combos of numbers that can be rolled using two dice. There are twenty-one unique combinations. But the number zero is always added up to the set, by way of "blanks," adding seven more bones, as the pieces are called. The widely used domino set carries twenty-eight pieces, the "heaviest" of which is 6-6. Sets are also designed that run up to 12-12, containing ninety-one bones, but they are seldom used.
The bones whose two ends are similar are also known as doublets. Each doublet belongs to one suit alone, while every other bone
belongs to two suits. In the set up to 6-6, there are seven bones in each suit, but eight ends of any one number. While between two bones, one is heavier than the other if it bears more dots, the other being lighter.To start any game, the bones are placed face down on the table and are shuffled by being moved about arbitrarily. Care must be taken not to face any domino in so doing. Every player draws a number of bones at random from this common pile, to form his hand. Dominoes are made thick and adequately heavy to stand on edge on the table.
For the first play, a bone is put
face up on the table. All succeeding bones played must be paired with those already down, generally by like numbers on one end of the bone played and an open end of the layout. For instance, if the first played is the 6-5, the next must bear a 6 or a 5 at one end and be placed against the other having like ends touching. An open end of the layout is one on which it is legal to play. The number of open ends changes with the particular game and also with the situations. Usually these ends are self-evident, being in fact the ends of various branches, but at times new branches may sprout from the sides of old.One target of a Domino game is invariably to get rid of all the bones in the hand. There could also be scoring in the course of play. The games are of two kinds based on the rule governing the play when a player has no playable bone. In the block game, he loses his turn. In the draw games, he draws bones from the common stock, called the boneyard, until he catches one that he can play.