A ruler, sometimes called a rule or line gauge, is an instrument used in geometry, technical drawing, printing, engineering and building to measure distances or to rule straight lines. The ruler is a straightedge which may also contain calibrated lines to measure distances.

https://en.wikipedia.org/wiki/Ruler

"There are all kinds of interesting questions that come from a knowledge of science, which only adds to the excitement and mystery and awe of a flower."
Richard Feynman
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