The Official Rules of Golf appear on the About.com Golf site courtesy of the USGA, are used with permission, and may not be reprinted without the permission of the USGA.

16-1. General
• a. Touching Line of Putt
The line of putt must not be touched except:

   (i) the player may remove loose impediments, provided he does not press anything down;
   (ii) the player may place the club in front of the ball when addressing it, provided he does not press anything down;
   (iii) in measuring — Rule 18-6;
   (iv) in lifting the ball — Rule 16-1b;
   (v) in pressing down a ball-marker;
   (vi) in repairing old hole plugs or ball marks on the putting green — Rule 16-1c; and
   (vii) in removing movable obstructions — Rule 24-1.

(Indicating line for putting on putting green — see Rule 8-2b.)

• b. Lifting Ball
A ball on the putting green may be lifted and, if desired, cleaned. The position of the ball must be marked before it is lifted and the ball must be replaced (See Rule 20-1).

• c. Repair of Hole Plugs, Ball Marks and Other Damage
The player may repair an old hole plug or damage to the putting green caused by the impact of a ball, whether or not the player’s ball lies on the putting green. If a ball or ball-marker is accidentally moved in the process of the repair, the ball or ball-marker must be replaced. There is no penalty, provided the movement of the ball or ball-marker is directly attributable to the specific act of repairing an old hole plug or damage to the putting green caused by the impact of a ball. Otherwise, Rule 18 applies.

Any other damage to the putting green must not be repaired if it might assist the player in his subsequent play of the hole.

• d. Testing Surface
During the play of a hole, a player must not test the surface of the putting green by rolling a ball or roughening or scraping the surface.

Exception: Between the play of two holes, a player may test the surface of any practice putting green and the putting green of the hole last played, unless the Committee has prohibited such action (see Note 2 to Rule 7-2).

• e. Standing Astride or on Line of Putt
The player must not make a stroke on the putting green from a stance astride, or with either foot touching, the line of putt or an extension of that line behind the ball.

Exception: There is no penalty if the stance is inadvertently taken on or astride the line of putt (or an extension of that line behind the ball) or is taken to avoid standing on another player's line of putt or prospective line of putt.

• f. Making Stroke While Another Ball in Motion
The player must not make a stroke while another ball is in motion after a stroke from the putting green, except that, if a player does so, there is no penalty if it was his turn to play.

(Lifting ball assisting or interfering with play while another ball in motion — see Rule 22.)

PENALTY FOR BREACH OF RULE 16-1:
Match play — Loss of hole; Stroke play — Two strokes.

(Position of caddie or partner — see Rule 14-2.)

(Wrong putting green — see Rule 25-3.)

16-2. Ball Overhanging Hole
When any part of the ball overhangs the lip of the hole, the player is allowed enough time to reach the hole without unreasonable delay and an additional ten seconds to determine whether the ball is at rest. If by then the ball has not fallen into the hole, it is deemed to be at rest. If the ball subsequently falls into the hole, the player is deemed to have holed out with his last stroke, and he must add a penalty stroke to his score for the hole; otherwise, there is no penalty under this Rule.

(Undue delay — see Rule 6-7.)

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