Abstract: A calligrapher's ruler including two fixed parallel longitudinal members each bearing a different set of graduated indicia is disclosed. A central member is slidably retained between the longitudinal members and mounts an elongated lateral straightedge member, also provided with a scale, so that the straightedge can be moved in a direction parallel to the longitudinal axes of the longitudinal members and maintained at a fixed angle, preferably perpendicular, relative thereto. A pointer on the central slide member is aligned with one of the indicia on the longitudinal members to establish the exact location of the straightedge member along the longitudinal members. A locking device on the central slide member locks the slide member and its connected straightedge in a selected position along the longitudinal members.