Below, is a list and description of some of the most popular optional rules for Backgammon, which you may come across, if you haven’t already, over the course of time. Some are more popular than others and each serves a different purpose. A general familiarity with the following ‘adaptations’ will help you if you ever arrive at a game where such rules are being used. Enjoy!
This rule stipulates that a player may immediately redouble and retain possession of the doubling cube when the offer to double is made by his opponent. It usually occurs when a player thinks his opponent has made an unwise doubling offer, and it is a way to dramatically increase the stakes of a game. Beavers are typically used in single-game Backgammon when money is at stake, and seldom permitted in tournament play.
The Crawford Rule
A rule used in match play, which states that when either player comes within one point of winning the match, the doubling cube cannot be used during the next game (which is referred to as the Crawford Game). This rule is used to avoid the situation in which a player who is two points away from victory, as compared to his opponent who is only one point away from victory, immediately redoubles because he has nothing to lose by doing so. The Crawford rule preserves the advantage that one player has gained by winning more matches than his opponent.
The Jacoby Rule
Stipulates that a finished game in which the stakes have been doubled or tripled (as a result of a gammon or backgammon, respectively) may only count if the doubling cube has been used at least once in the game. This rule deters a player with a large lead in a game from attempting to play on for the gammon or backgammon, when he could offer a double and most likely end the game. It is intended to speed up the game, and is typically used in money play, but not match play.
A rule, which states that upon the opening roll of a game (when each player rolls one die to determine who will play first) a doublet appears, the stakes of that game are immediately double. Therefore, if the players roll the same number three times in a row, the game would now be worth 8 times the original stakes. The doubling cube is placed in the middle and may be used by either player from this point on. Automatic Doubles must be agreed upon, and is typically used in money play only.