Insert 2x4 Ladder into both brackets, and drill through. Insert 3/8 inch diameter 3" long bolt. Affix with lock washer and nut. The mounting Brackets bolt to the end or side of the dock or deck or tree fort/house with four 3/8 inch diameter bolts (length varies dependent on structure). Tighten until teeth on the backside of the bracket are seated in the wood. The teeth can be ground off for use on an aluminum frame.
The part is approximately 4.5 inches by 4.5 inches by 3.75 inches and weighs about 2 pounds.
RDS has great pricing on stainless steel mounting hardware.