These 24 in T-Bar Brackets have an adjustable 8in height. They are used on metal or wood studs for box positioning in walls and ceilings. They are also used to mount boxes on ceiling T-bar grid and other structural members. Garvin Industries fixed length box bar hangers are available for 1-1/2 or 2-1/8 in D boxes. The locator dimples on the face of the bars allow for an exact positioning of single or multiple boxes. The dimple feature also provides quick start of screws and reinforcement to prevent the electrical box mounting screws from stripping out when boxes are being mounted. Garvin Industries adjustable brace design allows ground screw to clear when boxes are mounted. The boxes attach easily with self tapping screws, making the installation virtually effortless.