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This is a ruler with one of the ends raised, just like it has raised its head. After drawing a line with this ruler, you just need to gently press the raised head, and the ruler will rises without ruin the line from the ink marks. Even the ruler is hidden beneath the papers, you can still easily find it from the raised head.
It is can prevents ink marks, easy to pick up and easy to find.
Hubei University of Technology
Wuhan, China
Hubei University of Technology
Wuhan, China
Shi Yuanwu
Wu Chongxiang