Hummer 2007 H3 Owner's Manual page 56

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:
56
If the position you are
using does not have
a 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 head restraint and
you are using a
dual tether, route
the tether over the
seatback.
If the position you
are using has a fixed
head restraint and
you are using a
single tether, route
the tether over the
head restraint.