Ruler

:This article is about the drawing instrument. Ruler can also refer to a statesman in charge or ceremonial head of state of a country or minor politically significant principality; for this meaning see Monarch or Lists of incumbents.

Related Topics:
Monarch - Lists of incumbents

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A ruler is an instrument used in geometry and technical drawing to measure short distances and/or to rule straight lines. Strictly speaking, the ruler is the instrument used to rule and calibrated stick for measurement is called a measure. However, common usage is that a ruler is calibrated so that it can measure, creating ambiguity in what a ruler is allowed to do in Ruler-and-compass constructions.

Related Topics:
Instrument - Geometry - Technical drawing - Measure - Ruler-and-compass constructions

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For instance, a ruler with measurement capability (e.g. its own length) can be used for angle trisection. This is resolved by referring to an instrument that can only rule as a straightedge.

Related Topics:
Angle trisection - Straightedge

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Practical rulers have distance markings along their edges.

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How these distance markings are applied and calibrated should be described here, including a history of old methods.

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• A ruler makes a popular tool for use as a pervertible, i.e. for corporal punishment, usually on the hands (either outstretched palms or knuckles) or thighs. Generally, solid, heavy wooden or metal rulers are used for this purpose, but lighter, often flexible plastic ones can also be used punitively, especially in spanking.
• The ruler (calibrated, though numbers are not shown) appears as a charge in heraldry in the arms of Odouze.
 
Ruler: See also ►