Abstract: An adjustable square assembly has a framing square with orthogonal limbs, slide fittings for mounting on the respective limbs with an adjustable angle blade therebetween and a tri-square blade and body for adjustable mounting on one of the limbs so that the tri-square blade is in parallel with the other limb of the framing square. One limb of the framing square has a single groove which cooperates with one of the slide carriers as a means whereby the carrier can be adjustably clamped in place through a locking screw on the carrier. The other limb is wider and has a pair of grooves so that the other limb can take the slide carrier in one of the grooves and the framing square body in the other groove. All the parts are reversible so that the slide carriers can be mounted on either limb of the framing square and can operate either along the inner and outer edges of the respective limbs.