In a game of 501 the object is for one player or a team to be the first to reach zero from starting total of 501.
In simple terms, after three darts are thrown, the throwing player subtracts the total scored from his current total until he reaches zero.
In order to reach zero each player must finish by throwing a double i.e. if player one has 38 remaining he must hit double 19 to win, while if player two has 47 remaining he must hit single 7, double 20 to win – or a another combination of scores provided the final dart scores on a double.
Some versions of the game require a ‘double start’ whereby players must begin the game with a double as well as finishing on a double