Red, Chicago plenum, 2-1/8" deep, 4" square drawn boxes with (8) 1/2" & (4) 3/4" side knockouts and (3) 1/2" & (2) 3/4" bottom knockouts are installed in air plenum walls or ceilings for lighting fixtures, switches, receptacles or other outlet devices. They are painted red to easily distinguish them as fire alarm circuits. Square boxes are used to bring power to a number of electrical devices where multiple conductor runs are split in two or more directions. Garvin Industries’ 4S Boxes can be surface- or flush mounted when multi directional conduit runs are necessary.