A useful square for the quick location and marking of center on a round bar or disc.

The knife edge blade is made from spring steel, hardened and ground for extended life.

To use, hold the vee of the centre square against the circumference of the work piece (e.g. round bar). Scribe two lines at different angles on the work piece along the edge of the blade. The intersection of the scribed lines will be the center of the work piece.