Every part of the set is available separately, and the heads locate, slide and lock on to the rule to give precise squaring, centring and angular alignment with respect to the rule edge. Instructions are supplied with each part.,Rule: 11 3/4in/300 mm tempered steel rule with satin chrome finish. Subdivided to 1/64in. and 1mm on channel side, 1/32in. and 0.5mm on plain side.Square head: For right angle marking and try square work. Includes a spirit level and fine point steel scribe, and 45° mitre face.,Centre head: Locates centres on cylindrical faces.,Protractor: 0-180° scale (in both directions) graduated every 1°. Gives angular measurement from any edge. Includes spirit level.