Abstract: A tool for use by carpenters and the like for conveniently establishing a reference line on a working surface at a predetermined angular disposition from an established base line on said surface. The tool includes an elongated member from which angle lines or cords are each adapted to extend a predetermined distance such that the intersecting terminal ends of such cords in combination with the member, form a triangle having sides of known length. Inasmuch as the length of the triangle's sides are known, the angles included thereby are also known such that a chalked line connected to the member may be utilized to establish a reference line at a known angular disposition to the member. The tool has particular utility when it is desired to establish the angular relationship of a wall to be built with respect to an already existing wall.