Abstract: Elongated, one-piece molded plastic supports are affixed in vertically spaced relation to the front of a printed circuit card frame assembly backplane equipped with a plurality of card connector receptacles. Each support is formed having a forwardly facing tongue and groove formation along the length thereof which mates with a complementing tongue and groove formation formed along the rear edge of a one-piece molded plastic shelf. A retainer rod, inserted through aligned openings in the support and shelf tongues, sustains the assembly. Guide tracks in the upper and lower surfaces of vertically adjacent shelves accept printed circuit cards for plug-in electrical connection with the backplane receptacles.