| 摘要 |
PURPOSE: A blackboard ruler combined with a protractor is provided to enable measurement of an angle and a length and to ensure portability. CONSTITUTION: A blackboard ruler combined with a protractor comprises: a first fixed bar(110), a second fixed bar(120), a first withdrawal type measuring tape(130), a second withdrawal type measuring tape(140), and a protractor plate(150). The first fixed bar and the second fixed bar are detachably attached on the surface of a blackboard.
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