Abstract: A rack assembly for at least partially supporting a ladder in the bed box of a truck is disclosed herein. The rack assembly includes a telescopically erectable and collapsible stanchion assembly, at least one bracket assembly for mounting the bottom of the stanchion assembly to the truck's bed box, and a telescopically extendable and retractable crossbar assembly that is releasably securable at the top of the stanchion assembly. When the rack assembly is not being used, tubular sections of the stanchion assembly can be telescopically collapsed together. Tubular sections of the crossbar assembly can be released from the top of the stanchion assembly and then placed in the collapsed stanchion assembly. In this way, the rack assembly can be stored in a substantially unitary, reduced-volume configuration in the bed box of the truck.