GMC 1999 Envoy Owner's Manual page 112

Cargo Security Shade
You can use the cargo security shade to cover items in
the cargo area of your vehicle.
Grasp the handle and unroll the cover. Latch the posts
into the sockets on the inside trim panel on the
passenger's side of the vehicle to secure it.
CAUTION:
An improperly stored cargo cover could be
thrown about the vehicle during a collision or
sudden maneuver. You or others could be
injured. If you remove the cover, always store it
outside of the vehicle. When you put it back,
always be sure that it is securely reattached.
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Cargo Tie Downs
There are four cargo tie
downs in the rear that allow
you to strap cargo in and
keep it from moving inside
the vehicle.
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