Begin setup by constructing an exterior structural frame using one-inch welded steel square tubing, or assemble an equivalent frame using pre-drilled angle iron bolted with black hex hardware. Cut internal cabinet floor, roof, and divider panels from three-quarter-inch plywood, staining them with an odorless, low-VOC charcoal or dark walnut penetrating stain. Slide the stained wooden panels into the inner frame channels, fastening them securely from the underside with heavy-duty self-tapping structural metal screws. Cut black powder-coated steel diamond wire mesh sheets to size, sandwiching the mesh panels behind solid wood door frames and within the side cat portal cutout. Mount the doors using heavy exterior black steel strap hinges and vintage slide-bolt latches to emphasize the utilitarian aesthetic. Line the interior ceiling with acoustic felt tiles to deaden internal scratching noises, and apply two coats of clear satin polyurethane over all wood panels to protect against moisture.