Abstract: The invention is directed to a guide for a power saw or router of the type having a blade and a housing wider than the blade which directly overlies the blade during the cutting operation. The guide includes a guide bar having a straight outer edge configured for guiding a peripheral edge of the saw housing and a gauge device. The gauge device includes an elongated holder and a light beam projector mounted on the holder for projecting a beam of light at an angle relative to a lengthwise axis of the holder. In this respect, the light beam projector is mounted on the holder for projecting a beam of light at a right angle relative to a lengthwise axis of the holder such that the beam of light is parallel to the straight outer edge of the guide bar. The light beam projector is preferably a laser.