This instrument consists of a four-wheeled carriage, a scale arm graduated from 0-20 that is attached permanently to the carriage in a counterpoised condition about the pivot axis, and a scratch tool with a sharp circular rim mounted at 45° to the flat test surface.

• Simple pocket size tester
  
• Ideal for field use and demonstrations

To operate, attach riders to the scale arm at the numbered positions. The carriage is held down firmly by hand and moved in the opposite direction, to cause a trailing scratch. The large standard rider loads 100 g per division, while the small rider loads 25 g per division. This small rider may be used for making low-range measurements involving small increments of pressure, or it may serve as a vernier with the large rider in making more precise medium-range measurements.

• Scratch Hardness The force necessary to cut through the film to the substrate.
• Adhesion The force required to scrape a path through the film, when the stylus begins its motion on an uncoated portion of the panel.