A straight edge bar clamp comprises an elongated channeled bar, a threaded base, first and second movable jaw bodies, bosses or divots, a catching device, and a threaded shaft. The elongated channeled bar having an inner channel portion. The threaded base is installed fixedly in the elongated channeled bar. The first movable jaw body is installed movably and partially in the elongated channeled bar between the second movable jaw body and the end of the bar furthest from the threaded base. The bosses or divots are provided on an inner surface of the inner channel portion and configured to define the predetermined stopping positions of the first movable jaw body. The catching device is provided in the first movable jaw body. The second movable jaw body is installed partially in the elongated channeled base movably between the threaded base and the first movable jaw body along the elongated channeled bar.