a. To determine if it is unfit for play (Rule 5-3);
b. For identification (Rule 12-2), in which case it may be cleaned only to the extent necessary for identification; or
c. Because it is assisting or interfering with play (Rule 22).
If a player cleans his ball during play of a hole except as provided in this Rule, he incurs a penalty of one stroke and the ball, if lifted, must be replaced.
If a player who is required to replace a ball fails to do so, he incurs the general penalty under the applicable Rule, but there is no additional penalty under Rule 21.
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