This instrument measures hardness of protective coatings. The degree of hardness of paint films, plastic coatings, etc. can be accurately measured and recorded, no matter whether on a level or curved surface. The spring tension is set with the help of the slider. Holding the instrument upright and placing it's point on the test surface one draws a 5 to 10 mm long line at a rate of approx. 10mm p/sec. If the spring pressure is too high, the scratch is clearly visible: if too low, no scratch appears. By locking the slider every time one can control the applied pressure which is marked in Newtons. Thus, one can gradually approach the correct setting. Three scales are engraved into the pencil for the three pressure ranges:

1.0- 3N(accuracy 0.1 N), 20-10 N (accuracy 0-5 N), 3.0-20 N (accuracy 1.0 N).