Among the official USGA rules are governance of a player's behavior while a ball is in play and the condition of the clubs and balls. Player responsibilities regarding etiquette and knowledge of the rules are also stipulated.
According to USGA rules, a player is not allowed to interfere in any way with a ball that is in play. Likewise, he may not change physical conditions around a hole and thereby interfere with the playing of that particular hole. The penalties for breaching these rules may include loss of the hole, an assessment of two strokes or disqualification.
A player can start a particular round with a maximum of 14 clubs. During the round, he is limited to the clubs with which he began unless he started the round with less than 14. Partners may share clubs if the total number between the partners is 14 or less.
If a player's club is damaged in some way during the course of play, he may use it as it is or repair it if doing so does not delay the game. If the club is so damaged that the player cannot use it, he may replace the club.
A ball cannot be altered to affect the way it plays. Balls may not be cut, cracked or misshapen, but a ball is not deemed unfit due to mud or grass sticking to it or minor scratches resulting from normal play.
A player and his caddie bear the responsibility of knowing the rules; ignorance is not an excuse. Players must start at the allotted time. Each player must play the correct ball, so it is a good idea to place an identifying mark on it.