Ruler and moment were invented by China. They were two tools used by the ancients to measure and draw circles and squares. "Gauge" is a compass that draws a circle, and "moment" is a ruler with scales on it. That's what the ancients meant when they said, "If you don't obey the rules, you can't be Fiona Fang". It is impossible to find out the exact date of the invention of rules, but in Oracle Bone Inscriptions in the 5th century BC/KLOC-0, the words "rules" and "moments" already existed. Sima Qian, a famous historian in the Han Dynasty, recorded in Historical Records that when Yu Xia was managing water, he was "managing from the left, managing from the right". This shows that there were two tools: rules and moments in the era of Xia's water control (about 2000 BC).

The role of rules is of great significance to the development of ancient geometry in China. Shang Gao, a Zhou algebra scientist, once made a theoretical summary of "the method of using moments": "The flat moment is a straight rope, the moment is restrained and the height is expected, and the distance can be known by covering the moment and lying the moment." This sentence concisely summarizes the wide and flexible uses of moments.

The ancient Greeks generally used rulers and compasses when studying geometric problems. This ruler has no scale and can only draw straight lines. Greek painting can only start with the most basic tools-rulers and compasses, and complete as many geometric figures as possible. The study of drawing with ruler leads to the discovery of many mathematical theorems.