- Determine if it’s fit for play.
- Identify it (in which case it can be cleaned, but only enough to identify it).
- Prevent it from assisting or interfering with play.
- Penalties for violating Rule 20-1: One stroke, and the ball must be replaced.
21-1. The player can lift and clean his ball on the green, as long as he marks its position first. Off the green, the player may clean a lifted ball unless it’s been lifted to:
A ball on the putting green may be cleaned when lifted under Rule 16-1b. Elsewhere, a ball may be cleaned when lifted, except when it has been lifted:
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.
Exception: If a player incurs a penalty for failing to act in accordance with Rule 5-3, 12-2 or 22, there is no additional penalty under Rule 21.
