Starrett combination square set consists of a photo-engraved, hardened and tempered satin chrome steel blade, a square head, a centre head and a protractor head. The square head has a precision ground 90 degrees square face and 45 degrees miter face. It is used to make right angles and parallel lines and can also be used as a tri-square, miter, depth gage and height gage. The centre head is used to accurately locate centre of a cylindrical or square workpiece, whereas the protractor head features revolving turrets with direct-reading double graduations, ranging from 0 to 180 degrees, used to measure angles accurately. This combination square set features a reversible lock bolt, a scriber and a spirit level and comes in a fitted case. The reversible lock bolt enables the blade to be turned over without removing the lock bolt or nut and ensures proper alignment of the blade with the heads.