This section is from the book "How To Play Golf", by H. J. Whigham. Also available from Amazon: How to play golf.
Penalty for breach of this rule:
In Match Play, if the ball has not been dropped in strict accordance with the rule, the opponent has the option of having the ball dropped again.
In Medal Play, if the ball has not been dropped in strict accordance with the rule, the other competitor must call for the ball to be dropped again, and the player must comply or be disqualified.
The player must drop the ball himself, not his caddie nor his partner. A dropped ball shall not be considered in play until at rest.
When a ball is lifted from a hazard and dropped and falls back into the hazard, the player may lift again without further penalty.
When the balls in play lie within six inches of each other, measured from their nearest points, the ball nearer the hole shall be lifted until the other is played, and shall then be replaced as nearly as possible in its original position. Should the ball further from the hole be accidentally moved in so doing, it shall be replaced. Should the lie of the lifted ball be altered by the opponent in playing, it may be replaced in a lie near to, and as nearly as possible similar to, that from which it was lifted.
If the ball lie or be lost in water, the player may drop a ball under the penalty of one stroke.
When the ball lies in casual water on the putting green, it may be lifted without penalty and replaced by hand to one side but not nearer to the hole.
A ball in water in a hazard may be lifted and dropped behind the water or hazard, under penalty of one stroke.
Whatever happens by accident to a ball in motion, such as its being deflected or stopped by any agency outside of the match, or by the forecaddie, is a " rub of the green," and the ball shall be played from where it lies. Should a ball lodge in anything moving, such ball, or, if it cannot be recovered, another ball, shall be dropped as nearly as possible at the spot where the object was when the ball lodged in it. But if a ball at rest be displaced by any agency outside the match, the player shall drop it, or another ball, as nearly as possible at the spot where it lay. On the putting green the ball may be replaced by hand.
Penalty for breach of this rule: In Match Play, loss of the hole. In Medal Play, disqualification. Wind and weather are not agencies "outside the match."
If the player's ball strike, or be accidentally moved by, an opponent or an opponent's caddie or clubs, the opponent loses the hole.
Penalty incurred:
In Match Play, loss of the hole.
In Medal Play, no penalty.
If the player's ball strike the other competitor or his caddie or clubs, it is a "rub of the green," and the ball shall be played from where it lies. If the player's ball at rest be accidentally or intentionally moved by the other competitor or his caddie, the ball must be replaced.
If the player's ball strike or be stopped by himself or his partner or either of their caddies or clubs, or if, while in the act of playing, the player shall strike the ball twice, his side loses the hole.
Penalty for breach of this rule:
In Match Play, loss of the hole. In Medal Play, loss of one stroke.
If the player, when not making a stroke, or his partner or either of their caddies, touch their side's ball, except at the tee, so as to move it, or by touching anything cause it to move, the penalty is one stroke.
Penalty incurred:
In Match Play, loss of one stroke. In Medal Play, loss of one stroke.
Except at the tee, if the ball move while the player is addressing it, the player loses one stroke.
Except at the tee, if the ball be struck while moving, the penalty is one stroke, i. e., one stroke for the moving and one stroke for the play.
Except at the tee, if struck at while moving and missed, one stroke shall be counted for the moving and another for the miss.
Rule 26. A ball is considered to have been moved if it leave its original position in the least degree and stop in another; but if a player touch his ball and thereby cause it to oscillate, without causing it to leave its original position, it is not moved in the sense of Rule 25.
A player's side loses a stroke if he play the opponent's ball, unless: (1) the opponent then play the player's ball, whereby the penalty is canceled, and the hole must be played out with the balls thus exchanged; or (2) the mistake occur through wrong information given by the opponent, in which case the mistake, if discovered before the opponent has played, must be rectified by placing a ball as nearly as possible where the opponent's ball lay.
If it be discovered before either side has struck off at the tee that one side has played out the previous hole with the ball of a party not engaged in the match, that side loses the hole.
Penalty for breach of this rule:
1st Playing the opponent's ball with exceptions (1) and (2) above noted in the Rule:
In Match Play, loss of one stroke. The ball must be replaced.
In Medal Play, no penalty. The ball must be replaced.
2d. Playing out with the ball of a party not engaged in the match:
In Match Play, if discovered before the next tee stroke, loss of the hole.
In Medal Play, the player must go back and play his own ball, or, not finding it, return as nearly as possible to the spot where it was last struck, tee another ball and lose a stroke (Rule 5, Medal Play), or else be disqualified.
If a ball be lost, the player's side loses the hole. A ball shall be considered as lost if it be not found within five minutes after the search is begun.
 
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