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Ruler & Angle / Blackboard ruler

Ruler & Angle

"Ruler & Angle" by liquid Whenever always remain horizontal design carried out, when the ruler is rotated to maintain the level of liquid stationary state, can be directly pointed ruler tilt angle. Just a ruler can easily draw any horizontal angle on a blackboard (school many years of experience told me that appeared on the blackboard are basically horizontal).You do not have to borrow a protractor.


Zhongyuan University of Technology

Zhongyuan University of Technology
Henan.Zhengzhou, China