GMC Sierra 2018 Owner's Manual page 107

106 Seats and Restraints
anchor (loop) (1) at
the center rear
seating position.
3.2. For a top tether in the
rear center position:
3.2.1. Route the top
tether (4) through
the center loop (1),
and behind the
passenger side
headrest post.
3.2.2. Then attach the
top tether (4) to
the top tether
anchor (loop) at
the rear passenger
side seating
position.
3.3. For a top tether in the
rear passenger position:
3.3.1. Remove the
headrest.
3.3.2. Route the top
tether (4) through
the loop on the
passenger side.
3.3.3. Then attach the
top tether (4) to
the top tether
anchor (loop) (1) at
the center rear
seating position.
4. Tighten the top tether per the
child restraint manufacturer's
instructions.
When the top tether is properly
tightened, the anchor (loop)
may bend. This is normal and
will not damage the vehicle.
If child restraints are installed
in both outboard positions, both
top tethers can be attached to
the center loop. Top tethers
can be attached for child
restraints in all three rear
seating positions at the same
time, following the routing
instructions above.
5. Before placing a child in the
child restraint, make sure it is
securely held in place. To
check, grasp the child restraint
at the LATCH path and attempt
to move it side to side and
back and forth. There should
be no more than 2.5 cm (1 in)
of movement for proper
installation.
Headrest Removal and
Reinstallation
Crew Cab Models
For outboard rear seating positions,
if the child restraint cannot be
installed properly with the headrest
in place, the headrest may be
removed. See your dealer for
assistance with removal.
Store the removed headrests in a
secure place. Reinstall the headrest
before the seating position is
moved.