Rulers used in different situations have different requirements and standards. If the value is more accurate, it requires higher technology and must be produced by machine. In addition to the requirement of accurate value, the second key is the quality of the engraved value. Generally, a protective film will be applied after the engraved value. The third point is the selection of materials, which are now divided into plastic, metal and wooden rulers, Plastic rulers are mainly used for stationery by ordinary students, metal rulers are more used in industry, and wooden rulers are mainly used for teaching.