A storage unit assembly and method for office furniture units includes two end panels and a bottom panel configured to support objects thereon. A back stop rail is connected to end panels and the bottom panel. The back stop rail includes a lower web having a bottom flange and a center flange, wherein the bottom flange abuts the bottom panel of the storage unit, and the center flange extends above the bottom panel into the storage unit. An upper web is connected to the center flange, wherein the upper web extends upwardly and terminates at a top flange. A rear flange extends downwardly from the top flange, wherein the planar extent of the rear flange is substantially coplanar with the planar extent of the lower web.