What is the Jacoby rule?
The Jacoby rule says that a gammon or backgammon does not count extra unless the cube has been turned, that is, unless a double has been offered and accepted in the present game. The purpose of the rule is to avoid long games in which one player tries for a gammon rather than double the opponent out for one point. Technically, the Jacoby rule is optional, but its use in money play is very common. The Jacoby rule is never used in match play. The Jacoby rule is named for Oswald Jacoby, coauthor of The Backgammon Book, who proposed and promoted the rule. See post by Daniel Murphy.
