For a casual, non-competitive golfer, marking your ball may be just a simple courtesy to a player who’s farther from the hole, whether on the green or nearby. You just grab whatever's handy -- such as a plastic marker, a coin, or even a tee -- mark and remove your ball, then put it back when it’s your turn. But the rules of game apply to both amateur and professional golfers, and cover situations that involve something as simple as a ball marker.
Rules of Golf
The Professional Golfers' Association is among the organizations -- both pro and amateur -- that follow the Rules of Golf, as published by the United States Golf Association. Ball marking is referenced throughout the rules, but the most common points are covered under rules 20-1 and 20-3. Rule 20-1 states in part, “The position of a ball to be lifted should be marked by placing a ball-marker, a small coin or other similar object immediately behind the ball.” While there's no penalty for using an object that's not similar to a plastic ball-marker or a small coin, you'll rarely -- if ever -- see a PGA player use anything other than a small, flat disc to mark a ball.
Who May Mark a Ball
Under the Rules of Golf, a ball may be marked by a player, his partner (such as in a best-ball match) or “another person authorized by the player." The marked ball must then be replaced by the person who lifted the ball, the player, or the player’s partner. No matter who marks or replaces the ball, however, the player is responsible for any violations of the rules.
When Balls May Be Marked
In addition to marking balls on the green when another player is away, there are a variety of situations in which PGA players -- and anyone else following the official Rules of Golf -- are permitted to mark and lift their balls. If a player is unsure if a ball is his, he may mark and lift the ball for examination. If a ball is cut or otherwise damaged, he may mark and lift it, examine the damage and replace the ball if it’s unfit for play. On the green, a player may mark and lift the ball if he wants to clean it. If play is suspended due to threatening weather, a player may mark his ball’s position.
Just as a nation’s laws may be interpreted by courts, the Rules of Golf also has its equivalent to case law, which the USGA terms “Decisions.” For example, in the 2010 Dubai World Championship (not a PGA event, but played under the standard Rules of Golf), Ian Poulter marked his ball on the green of the second playoff hole, picked it up, then accidentally dropped the ball, which dislodged the marker. Poulter informed the match referee, who assessed Poulter a one-stroke penalty, costing him any chance to win the event (although he took home a second prize of $833,000).
Rule 20-1 states in part, “If a ball or ball-marker is accidentally moved in the process of lifting the ball … There is no penalty, provided the movement of the ball or ball-marker is directly attributable to the specific act of marking the position of or lifting the ball.”
In Dubai, however, the referee cited Decision 20-1/15, which narrows the definition of “directly attributable” to “the specific act of placing a ball-marker behind the ball, placing a club to the side of the ball, or lifting the ball such that the player's hand, the placement of the ball-marker or the club, or the lifting of the ball causes the ball or the ball-marker to move.” Since Poulter had lifted the ball away from the marker before he dropped it, the referee ruled that the ball was already marked when it slipped out of his hand, so dropping it wasn’t part of the act of marking the ball.