The referees maintain orderly and fair play on the court and administer the rules of the game to ensure that neither team has an unfair advantage. To make appropriate calls, referees must be observant and have exceptional knowledge of rules and playing styles. Referees must position themselves during play to afford a clear view of the action without interfering. A referee will cite rules infractions and stop play by blowing a whistle. After play has stopped, referees signal what violation has occurred by using hand signals and a verbal call. Most referees' decisions must be made very quickly. During the game a referee can run several miles supervising the activity, so exceptional physical fitness is important. Between games and during the off-season, referees engage in a continuing study of all possible game situations.