GMC 2008 Sierra 1500 Pickup Owner's Manual page 47

Some child restraints that have a top tether are designed
for use with or without the top tether being attached.
Others require the top tether always to be attached. In
Canada, the law requires that forward-facing child
restraints have a top tether, and that the tether be
attached. Be sure to read and follow the instructions for
your child restraint.
If the child restraint does not have a top tether, one can
be obtained, in kit form, for many child restraints. Ask
the child restraint manufacturer whether or not a kit
is available.
Lower Anchor and Top Tether Anchor
Locations
Rear Seat
i
(Top Tether Anchor): Seating positions with top
tether anchors.
j
(Lower Anchor): Seating positions with two lower
anchors.
The rear outboard seating positions have exposed
metal lower anchors located in the crease between the
seatback and the seat cushion.
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