Jacoby rule

The Jacoby Rule is named after the late great gamesman Oswald Jacoby. The Jacoby rule states that gammon and backgammon will come into effect if and only if the player has announced a double and it has been accepted by the opponent.

The Jacoby rule is normally used in Money play to encourage the players to win a) as quickly as possible and b) with as many points as possible. This increases the speed of the game when a player will not get stuck and wait for a possible gammon or backgammon win. To benefit from those he will have to double sooner or later and then the underdog is likely going to resign for a single loss.

When the game ends after one of the players has resigned or with a normal win, the loser pays the winner the initial stake multiplied by the value of the doubling cube and further multiplied by 2 (gammon) or 3 (backgammon). Therefore, if the original bet e.g. was 5 dollars and the winner won with a gammon and a double, he wins 20 dollars: 5 dollars x 2 x 2 = 20 dollars.

The Jacoby rule is never used in Match play, where the winner is the one acquiring a predetermined number of points in a series of games. In Match play gammon and backgammon are worth 2 and 3 points respectively, regardless whether the doubling cube has been used or not.