Rules

24. A Good Return
It is a good return:
a. If the ball touches the net, posts, singles sticks, cord or metal cable, strap or band, provided that it passes over any of them and hits the ground within the Court; or
b. If the ball, served or returned, hits the ground within the proper Court and rebounds or is blown back over the net, and the player whose turn it is to strike reaches over the net and plays the ball, provided that he does not contravene Rule 20(e); or
c. If the ball is returned outside the posts, or singles sticks, either above or below the level of the top of the net, even though it touches the posts or singles sticks, provided that it hits the ground within the proper Court; or
d. If a player's racket passes over the net after he has returned the ball, provided the ball passes the net before being played and is properly returned; or
e. If a player succeeds in returning the ball, served or in play, which strikes a ball lying in the Court.

USTA Comment: Paragraph e. of the rule refers to a ball lying on the Court at the start of the point, as a result of a service let or fault, or as a result of a player dropping it. If a ball in play strikes a rolling or stationary "foreign" ball that has come from elsewhere after the point started, a let should be played. See Case 7 under Rule 25 which pertains to an object other than a ball that is being used in the match.

ITF Note: In a singles match, if, for the sake of convenience, a Doubles Court is equipped with singles sticks for the purpose of a singles game, then the doubles posts and those portions of the net, cord or metal cable and the band outside such singles sticks shall at all times be permanent fixtures, and are not regarded as posts or parts of the net of a singles game.

A return that passes under the net cord between the singles stick and adjacent doubles post without touching either net cord, net or doubles post and falls within the court, is a good return.

USTA Comment: In doubles this would be a "through"-loss of point.

Case 1. A ball going out of Court hits a net post or singles stick and falls within the lines of the opponent's Court. Is the stroke good?
Decision: If a service: no, under Rule 10c. If other than a service: yes, under Rule 24(a).

Case 2. Is it a good return if a player returns the ball holding his racket in both hands?
Decision: Yes.

Case 3. The service, or ball in play, strikes a ball lying in the Court. Is the point won or lost thereby?
Decision: No. Play must continue. If it is not clear to the Umpire that the right ball is returned a let should be called.

USTA Comment: A ball that is touching a boundary line is considered to be "lying in the Court".

Case 4. May a player use more than one racket at any time during play?
Decision: No. The whole implication of the Rules is singular.

Case 5. May a player request that a ball or balls lying in his opponent's Court be removed?
Decision: Yes, but not while a ball is in play.

USTA Comment: This request must be honored.