Satin chrome blades and protractor heads Direct reading 0-180° in opposite directions, permitting the direct reading of angles and supplementary angles Reversible lock bolt allows choice of which graduated side of the blade faces the operator Non-reversible, meaning the blade is on the outside of the frame, so the frame stays on the same side of the workpiece Tempered steel blades with accurate, machine-divided graduations A spirit level indicates when the base reference surface is level Stable cast iron protractor head with black wrinkle finish.