2-1/8" deep 4" square boxes with (6) 1/2" & (4) BX side knockouts and a (1) 1/2" bottom knockouts are used when 4” square boxes must be mounted directly to wood or metal studs. They are installed in walls or ceilings for lighting fixtures, switches, receptacles or other outlet devices where flexible metal conduits are used. 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’ 4” square bracket boxes come with built in clamps for flexible metal conduits to speed up installation and save connector costs.