The R&A

Touching putting green - Repair or damage

During a round, you may take the following actions on the putting green, no matter whether your ball is on or off the putting green:

You may repair damage on the putting green without penalty by taking reasonable actions to restore the putting green as nearly as possible to its original condition, but only:
- By using your hand, foot or other part of your body or a normal ball-mark repair tool, tee, club or similar item of normal equipment, and
- Without unreasonably delaying play.

But if you improve the putting green by taking actions that exceed what is reasonable to restore the putting green to its original condition, you get the general penalty. “Damage on the putting green” means any damage caused by any person (including you) or outside influence, such as:

Ball marks, shoe damage (such as spike marks) and scrapes or indentations caused by equipment or a flagstick,
Old hole plugs, turf plugs, seams of cut turf and scrapes or indentations from maintenance tools or vehicles,
Animal tracks or hoof indentations, and
Embedded objects (such as a stone, acorn, hail or tee) and indentations caused by them.

But “damage on the putting green” does not include any damage or conditions that result from:

Normal practices for maintaining the overall condition of the putting green (such as aeration holes and grooves from vertical mowing),
Irrigation or rain or other natural forces,
Natural surface imperfections (such as weeds, bare or diseased areas or areas of uneven growth), or
Natural wear of the hole.

Related Rule - 13.1c(2)