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12.9 DELIBERATE HANDLING

The offense known as "handling the ball" involves deliberate
contact with the ball by a player's hand or arm (including fingertips,
upper arm, or outer shoulder).  "Deliberate contact"
means that the player could have avoided the touch but chose not to,
that the player's arms were not in a normal playing position at the
time, or that the player deliberately continued an initially accidental
contact for the purpose of gaining an unfair advantage.  Moving
hands or arms instinctively to protect the body when suddenly faced
with a fast approaching ball does not constitute deliberate contact
unless there is subsequent action to direct the ball once contact is
made.  Likewise, placing hands or arms to protect the body at a
free kick or similar restart is not likely to produce an infringement
unless there is subsequent action to direct or control the ball. 
The fact that a player may benefit from the ball contacting the hand
does not transform the otherwise accidental event into an infringement. 
A player infringes the Law regarding handling the ball even if direct
contact is avoided by holding something in the hand (clothing, shinguard,
etc.).

12.10 RULE OF THUMB FOR "HANDLING"

The rule of thumb for referees is that it is handling if the player
plays the ball, but not handling if the ball plays the player. 
The referee should punish only deliberate handling of the ball, meaning
only those actions when the player (and not the goalkeeper within the
keepers own penalty area) strikes or propels the ball with the hand
or arm (shoulder to tip of fingers).

12.11 USE OF THE SHOULDER

For purposes of determining deliberate handling of the ball, the "hand"
is considered to be any part of the arm-hand from fingertip to shoulder. 
Using the top of the shoulder is not considered as using the hand. 
(A diagram showing the area of the hand is shown below.)