The server must not serve until the other side is ready; ordinarily, the players of the receiving side are expected to be ready. During the game the player must not leave the court except in the act of playing, if he has an accident, or with the referee's permission for activities such as changing a racket, tying a shoelace, or tightening a belt. The referee normally grants a player's request for such activities, unless the ball is in play; however, he has the final right to refuse if he deems such activities delaying tactics.