GMC Envoy 2003 Owner's Manual page 115

Lower Position
Insert the front corners of the panel into the lower
guides and slide the panel forward. Press down on the
back of the panel to lock it in place. To prevent
soiling the carpet, the panel may be installed either
side up.
Notice: To help avoid damage, do not load objects
over 200 lbs. (90 kg) in this position. Failure to
follow this warning could damage the shelf.
Vertical Position
Insert the front corners of the panel into the vertical
guides behind the seatbacks and slide the panel down.
Plastic grocery bags can be attached to the hooks
on the panel.
Notice: When in vertical position, the shelf panel
should not be used as a barrier for large objects
in the cargo area when the seatbacks are
folded down.
2-47