As the playing time for each individual game is short, it is often played in matches, where victory is awarded to the first player to reach a certain number of points.
Setup
Each side of the board has a track of 12 long triangles, called points. The points are considered to be connected across one edge of the board, forming a continuous track in the shape of a horseshoe, and are numbered from 1 to 24. Each player begins with two checkers on his 24-point, three checkers on his 8-point, and five checkers each on his 13-point and his 6-point. The two players move their checkers in opposing directions, each from his own 24-point towards his 1-point.
Points 1 through 6 are called the home board or inner board, and points 7 through 12 are called the outer board. The 7-point is referred to as the bar point, and the 13-point as the mid point.
Movement
To start the game, each player rolls one die, and the player with the higher number moves first using the numbers shown. The players then alternate turns, rolling two dice at the beginning of each turn.
After rolling the dice a player must, if possible, move checkers according to the number of pips shown on each die. For example, if the player rolls a 6 and a 3 (noted as "6-3"), that player must move one checker six points forward, and another checker three points forward. The same checker may be moved twice as long as the two moves are distinct: six and then three, or three and then six, but not all nine at once. If a player rolls two of the same number, called doubles, that player must play each die twice. For example, upon rolling a 5-5 that player must move four checkers forward five spaces each.
In the course of a move, a checker may land on any point that is unoccupied or is occupied only by a player's own checkers. It may also land in a point occupied by exactly one opposing checker; such a lone piece is called a blot. In this case, the blot has been hit, and is placed in the middle of the board on the bar that divides the two sides of the playing surface. A checker may never land on a point occupied by two or more opposing checkers; thus, no point is ever occupied by checkers from both players simultaneously.
Checkers placed on the bar re-enter the game through the hitting player's home board. A roll of 2 allows the checker to enter on the 23-point, a roll of 3 on the 22-point, and so forth. A player may not move any other checkers until all checkers on the bar belonging to that player have re-entered the game.
When all of a player's checkers are in the player's home board, that player may start removing them; this is called bearing off. A roll of 1 may be used to bear off a checker from the 1-point, a 2 from the 2-point, and so on. A die may not be used to bear off checkers from a lower-numbered point unless there are no checkers on any higher points.For example if a player rolls a 6 and a 5, but has no checkers on the 6-point, though 2 checkers remain on the 5-point, then the 6 and the 5 must be used to bear off the 2 checkers from the 5-point. When bearing off, a player may also move a lower die roll before the higher even if that means 'the full value of the higher die' is not fully utilized. In other words if a player has exactly 1 checker remaining on the 6-point, and rolls a 6 and a 1, the player may move the 6-point checker 1 place to the 5-point with the lower die roll of 1, and then bear that piece off the 5-point using the die roll of 6, this is sometimes useful tactically.
If one player has not borne off any checkers by the time one's opponent has borne off all fifteen, then the player has lost a gammon, which counts for double a normal loss. If the losing player still has checkers on the bar or in the opponent's home board, then the player has lost a backgammon, which counts for triple a normal loss.
To speed up match play and to provide an added dimension for strategy, a doubling cube is normally used. The doubling cube is a six-sided die marked with the numbers 2, 4, 8, 16, 32, and 64. Before rolling the dice on his turn, a player may demand that the game be played for twice the current stakes. His opponent must either accept the new stakes or resign the game immediately. Thereafter, the right to redouble belongs exclusively to the player who last accepted a double. Whenever a player accepts doubled stakes, the cube is placed with the corresponding power of two facing upward.[13][14]
The game is rarely redoubled beyond four times the original stake, but there is no limit on the number of doubles. Although 64 is the highest number depicted on the doubling cube, the stakes may rise to 128, 256, and so on. In money games, a player is often permitted to "beaver" when offered the cube, doubling the value of the game again, while retaining possession of the cube.
The Jacoby rule
The Jacoby rule allows gammons and backgammons to count for their respective double and triple values only if the cube has already been offered and accepted. This encourages a player with a large lead to double, possibly ending the game, rather than to play it to conclusion hoping for a gammon or backgammon. The Jacoby rule is widely used in money play but is not used in match play.
The Crawford rule
The Crawford rule is designed to make match play more equitable for the player in the lead. If a player is one point away from winning a match, that player's opponent will always want to double as early as possible in order to catch up. Whether the game is worth one point or two, the trailing player must win to continue the match. To balance the situation, the Crawford rule requires that when a player first reaches a score one point short of winning, neither player may use the doubling cube for the following game, called the Crawford game. After the Crawford game, normal use of the doubling cube resumes. The Crawford rule is used in tournament match play.
