2006 Chevrolet Avalanche Owner's Manual - Page 154

To replace the drain grate do the following: Side Rail Channels The side rail channels are located on top of both sides of the cargo area. Flush them out with clean water debris collects inside of them. When loading cargo into the cargo area, be careful not to damage the rails. 1. Line up the clips on the vehicle with the slots in the grate. 2. When you are sure that the clips are aligned with the slots, push the grate down firmly. The grate should clip into place. Do not force the grate if it will not clip into place; realign the clips with the holes and try again. 2-80