If you are looking for a basic two piece L bracket this is NOT what you are looking for. The SIDE of your metal box should be scored/slotted. You would think the brackets would come with a simple chart, template or measurements for the cut/slot area. no And the company that makes these brackets won't give you that information either. However, the company that makes these mounts will sell you an expensive lawn mower sized router to cut the grooves/slots.