An apparatus having an enclosure that is mountable on a computer rack. The apparatus comprising: a U-shaped plate, two end-caps, and a module having three faces. The U-shaped plate comprising a channel and forming a bottom face and at least a portion of the front and back faces of the enclosure. The module, which has three faces, is configured to mate with the U-shaped plate via the channel. When the module is mated with the U-shaped plate, the three faces of the module form, at least partially, the top, front and back faces of the enclosure. The two end-caps are configured to be attached to the U-shaped plate at distal ends of the U-shaped plate, wherein, when the two end-caps are attached to the U-shaped plate, side walls of the end-caps form two side faces of the enclosure.