a child tasked with retrieving tennis balls from the court that have gone out of play. They also supply the balls to the players before their service so that the server can choose a suitable ball amongst them to serve with. Ball boys in "net" positions normally sit on their knees near the net and run across the court to collect the ball, while ball boys in the "back" positions stand in the back along the perimeter of the arena. Ball boys in the back are responsible for giving the balls to the player serving.