You can't use Fermat ruler in the senior high school entrance examination. Fermat ruler is a tool with various geometric patterns, which is often used to solve mathematical problems, such as grouping common triangles according to the relationship between time and half angle. However, during the senior high school entrance examination, candidates can only carry 2b pencils, 0.5mm black pens, erasers, liners, compasses, rulers and admission tickets. Fermat's ruler is regarded as a cheating tool because of its various geometric patterns, so it is not allowed to be brought into the examination room of the senior high school entrance examination. As a measuring tool, Fermat ruler is widely used in machining, architectural design, painting and other fields. It is said that this tool was invented by the French mathematician Fermat in the17th century, hence the name. When using Fermat ruler, you need to stretch it to the corresponding length according to the length to be measured, and clamp the object or drawing paper at two measuring points. At this time, by moving the ruler, the measuring point can be aligned with another measuring point, thus ensuring the accurate distance between the measuring points.