Clamps onto horizontal railings up to 2 inches thick, Easy to use hand knob makes installation easy, Extened arm hangs feeder away from railing to keep it clean, Feeder in picture is sold separately (HIATT38005), Attached to 1, 5 inch thick board, overall, depth: 32, 6, width: 10, 8, length: 1, 5 SKU: GC11449