RULE 21. Interference
If a player is hindered in making a stroke by anything not within his control, the point is replayed.
Comment: If a tree branch or a ball from another court should interfere with play, a let should be called immediately. However, if a player bumps into his own partner or is interfered with by a court fixture, that is not grounds for a let. In the situation covered by Rule 20b, if his opponent willfully hinders the player attempting to strike the ball, the player is entitled to the point by reason of interference, whether such interference is verbal or physical. However, if it is agreed that such interference was unintentional, a let should be called.
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