What is a straight or curved strip of wood, metal, etc., with a smooth edge, used for guiding a pen or pencil in drawing lines. Cf. Rule, n., 7 (a). Parallel ruler. See under Parallel called?

ruler — A straight or curved strip of wood, metal, etc., with a smooth edge, used for guiding a pen or pencil in drawing lines. Cf. Rule, n., 7 (a). Parallel ruler. See under Parallel. (Webster's 1913.)

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