Rule 15: Playing a Wrong Ball
A. In match play, if you play a ball that is not yours, you lose the hole unless the wrong ball is played in a water hazard; if you play a wrong ball in a hazard, you must then play the right ball.
B. In stroke play, if you play a ball that is not yours, you must take a two-stroke penalty unless the wrong ball was played in a water hazard. You must then play out the hole with your own ball. If you do not do so, you are disqualified.
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Rule 5: Changing Balls
Normally, you may not change balls during the play of a hole. There really is no set number of golf balls allowed each player per round of golf. A player may use a different ball to begin each of the 18 holes. However, they can not change balls during the playing of a hole unless the ball is lost or damaged. However, if you damage or cut your ball, you may do so after first telling your opponent or a fellow competitor.
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