| 摘要 |
PURPOSE: A ruler having a scale is provided to exactly measure an inner diameter of a structure by engraving a scale on the ruler case. CONSTITUTION: A ruler with a scale is C-shaped. The ruler measures a steel structure having an inner diameter of 150mm. A case of the ruler has a length of 70mm. The case of the ruler varies depending on the size of the ruler. The inner diameter of the steel structure is easily measured when the case is molded with a length of 70mm or 80mm. The case has a scale engraved on the case. When an inner diameter of a structure is measured, the end of the ruler is close to the one side of the inner diameter and the case is close to the other side of the inner diameter.
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