Abstract: An edge guided tool for scoring flat panels comprises a cutter assembly sliding on a track mounted on a conventional T-square vertical rail. A cutting tool body supporting a cutting plate over a panel to be cut is slideably mounted in the track on a resilient spring plate such that when the cutting blade is urged down toward the panel on the bending spring plate, the slide is urged against track sides to prevent further sliding, locking the slide and the blade in an alignment position. With the blade locked parallel to a T-square fence rail, as the T-square is moved with its fence rail abutted along a panel edge as a guide while the cutting blade is urged into the panel, the panel is scored along its length parallel to its length.