A ladder is one form of organising a tournament. A ladder is an open system, which means that everyone (who fulfils certain qualifications) can enter or exit the ladder at any time. The matches are independently arranged and carried out. The players' rating is mostly derived from the Elo-system, which awards the players points according to the played game. These points are set against the points awarded in the previous games. The calculated result then defines the player's rank. A ladder's main function is to determine the "best" teams, which are then able to work their way up to the Premiership.