Backgammon's Doubling Cube
To give an additional dimension for backgammon strategy and to speed up the game a doubling cube is commonly used. The doubling cube is described as die with 6 sides which are marked with the numbers 2, 4, 8, 16, 32 and lastly 64.
When a player has a belief that his position in the game is superior they can make a decision on their turn to double before rolling the dice which means that if the doubling cube is accepted, the current game being played is worth two times the current amount at stake or what the current stakes are.
A doubling cube is placed with two facing up to show everyone that the match's value being seen is doubled. The opponent could choose to either give his acceptance to the challenge of the doubling cube or resign from the match quickly.
After accepting the doubling cube, a player now has the right to redouble if they feel the odds have turned and they are now in a favorable position. When the redouble happens, the cube is positioned showing the next power of two. From 2 to 4, as an example.
The match is redoubled rarely more than four times its' original stake, however there is no limit theoretically on the number of redoubles that could be made. Even though 64 is indeed the highest number for doubling the cube as depicted, the stakes could rise up to 128 or 256 even 512 and so forth, it all depends on how much the players wish to risk.
With money matches, a backgammon player is usually allowed to beaver when being offered a double, then doubling the value of the match again while at the same time retaining the hold of the cube.
The Jacoby rule is a rule which allows the gammons and the backgammons to count as their respective triple or double values only if there has been at least a use of the doubling cube within the match. The rule convinces the player with the largest lead in the match to double, in the hope of possibly ending the game rather than to play to the very end in hopes of backgammon or a gammon. This rule is widely used everywhere with money played but rarely used in matches.
The Crawford rule is the rule which is designed to create match play fairer to the player leading the game. This action is done if the player leading the match happens to be a single point away from becoming the winner of the game. The opposing player will get no opportunity to not choose to double.
The result of the match will not be affected but to balance one point away from winning a match. His opponent has no incentive not to double; even if the game contains the value of one point or two points, and in order to make the situation balance. The Crawford rule would require that when a player reaches the score one point short from winning the game, nobody could use the doubling cube for the next game.
This is what the Crawford game is all about but afterwards the doubling cube's normal use resumes again. This game is also used in most of the match plays.