Aluminum cleats can be used for indoor and outdoor installations
A Heavy-Duty Cleat Hanger set includes one long 36 inch extruded aluminum cleat that is mounted on the wall and three short 2 1/2 inch cleats with a matching profile (shape) that are mounted just down from the top edge of the back side of the object being hung.
pre-drilled 7/32" holes in cleats will accept up to a #10 pan-head screw