GMC 2010 Acadia Owner's Manual page 114

3-60 Seats and Restraints
2. If the child restraint manufacturer
recommends that the top tether
be attached, attach and tighten
the top tether to the top tether
anchor, if the vehicle has one.
Refer to the child restraint
instructions and the following
steps:
2.1. Find the top tether anchor.
2.2. If the anchor is covered, flip
open the cover to expose
the anchor.
2.3. Route, attach and tighten
the top tether according to
your child restraint
instructions and the
following instructions:
If the position you are using
does not have a headrest
or head restraint and you
are using a single tether,
route the tether over the
seatback.
If the position you are using
does not have a headrest
or head restraint and you
are using a dual tether,
route the tether over the
seatback.