GMC Terrain 2010 Owner's Manual page 80

2-54 Seats and Restraints
1.3. Attach and tighten the lower
attachments on the child
restraint to the lower
anchors.
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 equipped. Refer to the
child restraint instructions and
the following steps:
2.1. Find the top tether anchor.
2.2. 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.