The Doubling Cube

A doubling cube is a die marked with the numbers 2, 4, 8, 16, 32, and 64.  It is used for gambling, with the face-up value signifying the multiple of the original stake set at the start of a game that the winning player, wins at the end. 

Whenever a player thinks he can win the game during the course of play, he may double the stakes initially set at the start of a game.  The player must do this when it is their turn and before he has rolled his dice.  The doubling is signified by turning the doubling cube so that the multiple value is face-up.  So, if the doubling cube has a 2 face-up the winner is paid double the initial stake, and if the doubling cube has 4 face-up the winning player receives 4 times the original stake, and so on for 8, 16, 32, and 64.  The other player must agree to doubling the stakes before it can take effect.  If the other player doesn't agree to the doubling, he forfeits the game. There is no limit to the number of times the initially agreed stake can be doubled.

Gammons and Backgammons

If a player hasn't borne-off any checkers before their opponent has borne-off all of theirs, then the player is said to have been "gammoned" and loses twice the value of the doubling cube.  However, if a player still has any of their checkers on the bar or in their opponents home-board they are said to have been "backgammoned" and lose three times the value of the doubling cube.

Optional Rules

The following rules are in  fairly widespread use by many Backgammon players.

• If two identical values are thrown with the players initial throw when deciding who goes first, then the stakes are automatically doubled.  The doubling cube is turned so 2 is face-up and kept halfway between the two players.  Automatic doubling like this is usually limited to one time per game.
• A player who has doubled using the doubling cube may immediately double again as long as they haven't picked up their dice.  Their opponent must agree to the doubling, as with a single double, before it takes effect.  This is known as a "Beaver".
• A gammon or backgammon isn't counted as double or triple when neither player has offered to double with the doubling cube.  This rule is meant to speed up play, preventing players from not doubling and trying for a gammon.  Known as the "Jacoby" rule because it was Oswald Jacoby, a Backgammon author, who invented and promoted the rule.  Commonly used in money games but never in match play.

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