Chevrolet 2003 Avalanche Owner's Manual page 144

5. Push the latches away from you (start with the left
latch) to lock the panel in place. You should hear a
click when each latch locks correctly.
6. Install cargo cover 3 next. Place the latches in the
open (unlocked) position. Place the cargo cover
panel on the cargo area rails while holding the back
of the cargo panel up.
2-70
Left Side Shown, Right Side Similar
Push the panel forward until it is snug against the
other panel and then let the back of the panel down
being sure that the alignment pegs align with the
receivers (see arrow).