Ruler (Ruler) Ruler or ruler is a commonly used long gauge. This measuring instrument has the smallest scale of 1 mm or 0.1 cm. The Ruler has a measurement precision of half of its smallest scale of 0.5 mm.
When measuring with the ruler, the direction of sight must be perpendicular to the scale on the ruler and the measured object. If not perpendicular it will cause errors in the measurement, may be greater or less than the original size.