As shown in FIG. 1, in this embodiment, each vertical support unit 104 includes one front elongated vertical member 106, one rear elongated vertical member 108 and a plurality of front-to-rear elongated members 110 that extend in part in a depth direction (i.e., front-to-rear direction) of the rack-supporting frame 102 and interconnect the front and rear elongated vertical members 106, 108. In this embodiment, the front-to-rear elongated members 110 extend generally horizontally but they may extend diagonally in other embodiments. For instance, each front-to-rear elongated member 110 may extend either upwardly and rearwardly or downwardly and rearwardly from a front vertical member 106 to a corresponding rear vertical member 108 that is laterally aligned with that front vertical member 106. The vertical support units 104 could be configured differently in other embodiments.

With reference to FIGS. 2 to 4, each rack 10 has a left lateral end 14 and a right lateral end 16 which are opposite one another in the lateral direction. A front end 18 is disposed on a front side of the rack 10 and a rear end 20 on a rear side of the rack 10. As can be seen, the rack 10 has a greater width, measured between the lateral ends 14, 16, than a height thereof, measured between a lower end 17 and an upper end 19 of the rack 10. As such, the rack 10 can be said to be horizontally-extending rather than vertically-extending.