GMC Sierra 2014 Owner's Manual page 116

3-56 Seats and Restraints
To reinstall the headrest:
1. Insert the headrest posts into the
holes in the top of the seatback
with the longer chrome plated
post toward the driver side of the
vehicle.
2. Push the headrest all the way
down until it contacts the top of
the seatback.
Double Cab Models
The rear outboard headrests should
be removed when installing forward
facing child restraints.
To remove the headrest:
1. Press both buttons on the
headrest posts and pull up on
the headrest.
2. Store the headrest in a secure
place.
3. When the child restraint is
removed, reinstall the headrest
before the seating position
is used.
To reinstall the headrest:
1. Insert the headrest posts into the
holes in the top of the seatback
with the longer chrome plated
post toward the driver side of the
vehicle.
2. Push the headrest all the way
down until it contacts the top of
the seatback.