An apparatus for increasing the cargo capacity of a pickup truck cargo bed area is disclosed. The apparatus has a base plate attached to the interior side of the tailgate of the pickup truck. A flat rectangular end-wall plate is pivotally attached the base plate. The end-wall plate has pivotally attached sidewall plates that fold, with the end-wall plate, onto the base plate. The truck cargo area is provided with adjustable mounting brackets to secure the sidewall plates to the truck cargo bed area when the apparatus is deployed for use. The apparatus may be folded and secured on the tailgate when it is not in use and unfolded and attached to the sidewall mounting brackets for deployment and use.