Abstract: An adjustable jig includes rigidly formed arms that have rectilinear shapes provided with opposite edges, an elongated central opening formed therein and opposed ends abutted with adjacent arm ends. Fasteners are interfitted within the arm openings such that the arms become statically affixed to each other and are detachable from associated ones of the openings. Each fastener includes a tri-lobed nut that has a threaded bottom end. A cap is conjoined to the threaded bottom end and has an outwardly beveled perimeter converging upwardly towards a bottom surface of one of the arms. Each arm has two of the fasteners interfitted through the opening associated therewith. A level gauge is included for establishing a horizontal plane along one arm and is releasably conjoined to a top surface of one arm and positioned at an interior edge thereof.