GMC 2009 Sierra - Manual (Page 12)

Head Restraints
Adjust the head restraint so that the top of the restraint
is at the same height as the top of the occupant’s
head. This position reduces the chance of a neck injury
in a crash.
Pull the head restraint up
to raise it. To lower the
head restraint, press the
release button (A), located
on the top of the seatback,
while you push the head
restraint down.
The front seats may have head restraints that also tilt
forward and rearward.
To tilt the head restraint, grasp the top of the restraint
while pressing the button (B), located on the inboard
side of the head restraint, and move it forward or
rearward until the desired locking position is reached.
Try to move the head restraint after the button is
released to make sure that it is locked in place.
The second row seats may have head rests that can be
adjusted up and down, but they do not tilt.
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