Buick 2009 Enclave - Manual (Page 43)

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.
If the position you are using
has a fixed headrest or head
restraint and you are using a
dual tether, route the tether
around the headrest or head
restraint.
Seats and Restraint System 1-39