GMC 2016 Yukon XL Denali Owner's Manual page 100

If the position you are
using has a fixed head
restraint and you are
using a single tether, route
the tether around the
inboard or outboard side
of the head restraint.
If the position you are
using has a fixed or an
adjustable head restraint
and you are using a dual
tether, route the tether
around the head restraint.
3. 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.
Head Restraint Removal and
Reinstallation
1. Partially fold the seatback
forward. See Third Row Seats
0 63 for additional information.
Seats and Restraints
2. Press the buttons on the head
restraint posts and pull up on
the head restraint.
3. Route the top tether of the child
restraint under the head
restraint.
99