Quiet Glide Flat Rail Mounting Drill Bit, 5/16-9, 4-1/2" OAL. High Speed Steel Bright Finish designed for use on steel, stainless steel (300 and 400 series), cast iron, aluminum, copper, and brass. Use this bit with flat rail rolling door assemblies for wall mounting. Quiet Glide Flat Rail Mounting Drill Bit, 5/16-9, 4-1/2" OAL. High Speed Steel Bright Finish designed for use on steel, stainless steel (300 and 400 series), cast iron, aluminum, copper, and brass. Use this bit with flat rail rolling door assemblies for wall mounting.