regla2

² = scale, ruler.

Ex. The apparent size of the face is measured directly with a finely graduated scale and a magnifying glass.

Ex. Scientific equipment for the examination of rare books, manuscripts, and documents include four items found in every library and private study -- micrometer calipers, view finders, dividers and rulers.

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* regla de cálculo = slide rule.

* regla de componer = setting rule.

* regla muy precisa = finely graduated scale.