Rules

25. Hindrance of a Player
In case a player is hindered in making a stroke by anything not within his control, except a permanent fixture of the Court, or except as provided for in Rule 21, a let shall be called.

USTA Comment: See Rule 13 and its USTA Comments regarding lets.

Case 1. A spectator gets into the way of a player, who fails to return the ball. May the player then claim a let?
Decision: Yes. If in the Umpire's opinion he was obstructed by circumstances beyond his control, but not if due to permanent fixtures of the Court or the arrangements of the ground.

Case 2. A player is interfered with as in Case No.1, and the Umpire calls a let. The Server had previously served a fault. Has he the right to two services?
Decision: Yes. If the ball is in play, the point, not merely the stroke, must be replayed as the Rule provides.

Case 3. May a player claim a let under Rule 25 because he thought his opponent was being hindered, and consequently did not expect the ball to be returned?
Decision: No.

Case 4. Is a stroke good when a ball in play hits another ball in the air?
Decision: A let should be called unless the other ball is in the air by the act of one of the players, in which case the Umpire will decide under Rule 21.

Case 5. If an Umpire or other judge erroneously calls "fault" or "out", and then corrects himself, which of the calls shall prevail?
Decision: A let must be called unless, in the opinion of the Umpire, neither player is hindered in his game, in which case the corrected call shall prevail.

Case 6. If the first ball served-a fault-rebounds, interfering with the Receiver at the time of the second service, may the Receiver claim a let?
Decision: Yes. But if he had an opportunity to remove the ball from the Court and negligently failed to do so, he may not claim a let.

Case 7. Is it a good stroke if the ball touches a stationary or moving object on the Court?
Decision: It is a good stroke unless the stationary object came into Court after the ball was put into play in which case a let must be called. If the ball in play strikes an object moving along or above the surface of the Court a let must be called.

Case 8. What is the ruling if the first service is a fault, the second service correct, and it becomes necessary to call a let either under the provision of Rule 25 or if the Umpire is unable to decide the point?
Decision: The fault shall be annulled and the whole point replayed.