Rule 20

It seems such a simple matter, but there are considerations about placing and replacing a ball that golfers should be aware of. I hope that you find this question and answer format useful.

What is the difference between placing and replacing?
Sometimes the Rules require a ball to be ‘placed’ at a different spot from where it came to rest (e.g. after a ball has been dropped and re-dropped under penalty from an unplayable lie and it has again rolled to a place that makes the drop invalid, it must then be placed at the spot where it first struck a part of the course when re-dropped). When the Rules require that the ball is put back at the same spot that it was lifted from it is being ‘replaced’ (e.g. having been marked and lifted from the putting green).

Who may place and replace a ball?
A ball to be placed under the Rules must be placed by the player or his partner. A ball to be replaced under the Rules must be replaced by any one of the following: (i) the person who lifted or moved the ball, (ii) the player, or (iii) the player’s partner.

Is there a penalty if I move my ball-marker while replacing my ball, or move my ball when I am placing my ball marker?
There is no penalty, providing the movement of the ball or ball-marker is directly attributable to the specific act of placing or replacing the ball or removing the ball-marker. However, if you accidentally drop your ball on your ball-marker, causing it to move, then you incur a penalty, as Ian Poulter found to his cost in Dubai in November, 2010. (Click on this link for the details).

What must I do if the original lie of my ball on a fairway or in the rough has been altered?
The ball must be placed in the nearest lie most similar to the original lie that is not more than one club-length away, not nearer the hole and not in a hazard.

What must I do if the original lie of my ball in a bunker has been altered?
The original lie must be re-created as nearly as possible and the ball must be placed in that lie.

What must I do if it is impossible to determine the spot where the ball is to be placed or replaced (e.g. someone wrongly played my ball while I was some way away from it and they threw it back to me)?
If the ball was lying through the green it must be dropped as near as possible to the place where it lay, but not in a hazard or on a putting green; if it was in a hazard, the ball must be dropped in the hazard as near as possible to the place where it lay; if it was on the putting green, the ball must be placed as near as possible to the place where it lay, but not in a hazard.

What must I do if my ball will not come to rest at the spot that I have to place or replace it?
The ball must be placed at the nearest spot where it will come to rest that is not nearer the hole. If it was in a hazard that spot must be in the hazard, if it was not then it must not be placed in a hazard, even if that is where the nearest point is.

What must I do if, after I have placed my ball at rest, it subsequently moves?
The ball is in play as soon as it is at rest, so it must be played from where it moves to, without penalty, whether that is nearer to the hole or farther away from it.

May I (re)place my ball more than once?
If you have replaced your ball at a marker on the putting green you may mark and lift it again (e.g. to line-up markings on the ball to the line of putt). However, a ball that has been (re)placed off the putting green (e.g. when a Local Rule for Preferred Lies is in operation) may not be lifted again once it has come to rest after placing, because it is in play.

What is the penalty if I wrongly substitute a ball when placing or replacing it (i.e. exchange the original ball with another ball)?
The penalty is two strokes in stroke play or loss of hole in match play.

What is the penalty if I drop a ball that should have been placed, or place a ball that should have been dropped?
The penalty is two strokes in stroke play or loss of hole in match play.

What is the penalty if a ball that is to be placed or replaced is placed other than on the spot from which it was lifted or moved and the error is not corrected?
The penalty is two strokes in stroke play or loss of hole in match play.

If I place my ball at the wrong spot may I correct the error before making my stroke?
Yes, A ball placed at a wrong spot but not played may be lifted, without penalty, and the placed at the correct place (Rule 20-6). 

 
So, placing and replacing is not such a simple matter and can incur unnecessary penalties if not carried out according to the Rules!