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The longer scale line of ruler can draw vertical lines faster and accurately.In common,the most people always draw vertical lines by aiming at the lines offered.But the scale line of common ruler is not long enough,which leads to the big error and low efficiency.This design can solve this cast and draw paraller lines without other tools.
Wuhan university of science and technology
Wuhan in Hubei, China
huan Yang,
Wuhan university of science and technology
haiqin chen,
Wuhan university of science and technology
yang Zhang,
Wuhan university of science and technology