Rules

7. The Service
The service shall be delivered in the following manner. Immediately before commencing to serve, the Server shall stand with both feet at rest behind (i.e. further from the net than) the base-line, and within the imaginary continuations of the center-mark and side-line. The Server shall then project the ball by hand into the air in any direction and before it hits the ground strike it with his racket, and the delivery shall be deemed to have been completed at the moment of the impact of the racket and the ball. A player with the use of only one arm may utilize his racket for the projection.

USTA Comment: There is no restriction regarding the kind of service which may be used; that is, the player may use an underhand or overhand service at his discretion.

Case 1. May the Server in a singles game take his stand behind the portion of the base-line between the side-lines of the Singles Court and the Doubles Court?
Decision: No.

USTA Comment: In singles, the server may stand anywhere in back of the baseline between the imaginary extensions of the center mark and the singles sideline.

Case 2. If a player, when serving, throws up two or more balls instead of one, does he lose that service?
Decision: No. A let should be called, but if the Umpire regards the action as deliberate he may take action under Rule 21.