Tennis officials are an integral part of the game. Linesmen, also known as line judges, are responsible for making calls on whether a ball is in or out of bounds. They are usually positioned at the ends of the court and have the authority to overrule the umpire's decision. Umpires, or referees, are the highest authority on the court and are responsible for making all final decisions. They are the only ones who can award points and declare a winner.