Abstract: A square for laying out and marking run and rise lines on supporting stringers for a staircase has a rake bar connected to slots near the ends of blades of the square. Markings showing a range of horizontal run distances are placed on the outer edge of the long blade of the square, and markings showing vertical rise distances are given on the outer edge of the short blade. The rake bar has a contact surface perpendicular to the plane of the square and has one end alignable with a marking corresponding to a selected run distance and the other end alignable with a rise distance marking. Once aligned, the bar is held in position against the blades by a pair of bolts. Placement of the adjusted tool with the rake bar contact surface flush against a side edge surface of a stringer results in outer edges of the blades being put in positions where horizontal and vertical cuts are to be made in the stringer.