GMC 2008 Envoy Denali Owner's Manual page 47

The labels are located above a flap, at the base of
the seatback, in the rear outside seating positions. The
anchors are located under the flap. In order to get to the
anchors you will need to pull the strap at the center of the
seat where the seat cushion meets the seatback. This will
allow you to fold the seat cushion up and out of the way.
Lift the flap to expose the anchors and then lower the
seat cushion. Be sure the cushion is locked into place.
To assist you in locating
the lower anchors, each
seating position with lower
anchors has two labels,
near the crease between
the seatback and the
seat cushion.
The top tether anchors for each rear seating position
are located on the floor in the cargo area of your vehicle.
Do not use the rear tie-down brackets near the liftgate
for attaching top tethers. Be sure to use an anchor
located on the same side of the vehicle as the seating
position where the child restraint will be placed.
Do not secure a child restraint in a position without a
top tether anchor if a national or local law requires that
the top tether be attached, or if the instructions that
come with the child restraint say that the top tether
must be attached.
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