As found on page 20 of the 2006-07 USGA Rules of Golf.
In Stroke play, if a competitor is doubtful of his rights or the correct procedure during the play of a hole, the player may, without penalty, complete the hole with two balls. After the doubtful situation has arisen and before taking further action, the competitor must announce to his marker or a fellow-competitor that he intends to play two balls and which ball he wishes to count if the Rules permit. If he fails to do so, the provisions of Rule 3-3(ii) apply. The competitor must report the facts of the situation to the Committee before returning his scorecard. If he fails to do so, he is DISQUALIFIED!
