Chevrolet 2008 Avalanche Owner's Manual page 158

Always use the storage strap system to store the
cargo panels during driving.
Before storing the cargo panels, be sure that the
latches are in the locked position. The latches are
in the locked position when they are parallel to
the front and back edge of the panel.
Use the following instructions for the proper storage
sequence and location for each panel:
A. Secure clip A on the secondary strap.
B. Secure clip B on the secondary strap.
C. Place the remaining primary straps on top of the
lid and tray.
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2. Starting with cargo panel 1, load the cargo panel
with latches up and facing away from you.