Rulers are commonly used for people for a variety of purposes, especially in design or architecture. Drawing and switching between lines or angles is a frequent affair that requires switching between different kinds of rulers in an inconvenient and tedious manner. With this ruler, the user can switch between a straight ruler and a 90-degree-angle ruler quickly without changing measuring tools.
The ingenious ruler consists of a shaft and two pieces of identical trapezoids on the other side, of 45-degree angle and 135-degree angle respectively. The user only has to rotate one part of the ruler and instantly lock it in a 90-degree angle, and rotate it back to form a straight ruler. With this principle, the user gets a 90-degree angle with two 45-degree angles, or a 180-degree angle with a 45-degree and a 135-degree angle.
Chen Songqin, Luo Xijun, Ning Yixing, Tian Qijun, China