Extension Brackets / 1175 The all-steel extension bracket is protected with a durable black polyester powder coat to prevent corrosion. Eight inches of vertical pole clearance are required for installation. It can be installed on all types of poles. Slots are provided for banding to cement, steel, or fiberglass poles. For mounting to wood poles, standard bolt holes are available for use with 5/8" thrubolt and two 1/2" x 4" drive-type lag bolts, not supplied.