If a player is hindered in playing the point by a deliberate act of the opponent(s), the
player shall win the point.
However, the point shall be replayed if a player is hindered in playing the point by
either an unintentional act of the opponent(s), or something outside the player’s own
control (not including a permanent fixture).
An unintentional double hit is not a hindrance.
It is not a hindrance if a player stops playing a point because he believed his opponent is being hindered. In this case the player loses the point.
If a ball in play hits a bird, this is considered a hindrance and the point is replayed.
It is not considered a hindrance if a ball, or other object, which was on the player’s side of the court at the beginning of the point hinders play.
In doubles the server’s partner may stand anywhere on their side of the net (inside, or outside of the court lines). However if a player is creating a hindrance to the opponent the hindrance rule is to be observed.