... , case hardened, surface hardness HV450-750, core hardness HV27 Window Frame Screw1) Application: it is for the installation of windows and ... PVC-U, wood or aluminium, as well as frame couplings and brackets. Window frame screws tap directly into brickwork, doing away with ... . They provide a secure fixing into a wide rang of materials since they are suitable for concrete, solid re brick, hollow ...