GMC 2001 Yukon XL Owner's Manual page 68

Suburban/Yukon XL Third Row Seat
Utility models: A child restraint with a top strap
should only be used in the second row. Don't use a child
restraint with a top strap in the right front passenger's
position or in the third row, because there's no place to
anchor the top strap.
An anchor loop bracket for a top strap is located at the
bottom rear of the seat cushion for each seating position
in the second row.
Utility Second Row Seat
Anchor the top strap to one of these anchor points.
Be sure to use an anchor point located on the same
side of the vehicle as the seating position where the
child restraint will be placed. Raise the head restraint
and route the top strap under it.
Once you have the top strap anchored, you'll be ready
to secure the child restraint itself. Tighten the top
strap when and as the child restraint manufacturer's
instructions say.
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