| 摘要 |
PROBLEM TO BE SOLVED: To provide a center line ruler which enables easy determination of the center of a circle of a column, an elliptic cylinder or the like and is capable of determining the central point by drawing two center lines and which can be stored compactly. SOLUTION: The length and the width of a quadrilateral comprised of movable points of expansion and contraction are made equal and the center line ruler is fitted between the points of expansion and contraction in a pair. The center line ruler rotates around and slides at the individual points so that it holds a measuring object. Thereby the center line can be determined, while the central point can be determined by determining two of the center lines by rotating the measuring object.
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