GMC 2010 Canyon Crew Cab Owner's Manual page 82

2.2. Route the top tether according to your child
restraint instructions and the following
instructions:
2-54
If the position you are using
has a fixed headrest or
head restraint and you are
using a single tether, route
the tether over the head
restraint.
If the position you are using
has an adjustable headrest
or head restraint and you
are using a single tether,
raise the headrest or head
restraint and route the
tether under the headrest
or head restraint and in
between the headrest or
head restraint posts.
If the position you are using
has a fixed or adjustable
headrest or head restraint
and you are using a dual
tether, route the tether
around the headrest or
head restraint.
2.3. Attach the top tether to the anchor (A). Make
sure that you secure the top tether to the
top tether anchor and not to the seatback
latch (B).
2.4. Push rearward on the seatback until it locks
into its upright position. Push and pull on
the seatback to make sure it is secured
properly.