Ruler Ruler Sukhoi Su-27 Category="Dimensional instruments"Category="Measuring tools and gauges"Category="Spanking implements"
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.

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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. 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.

Practical rulers have distance markings along their edges. How these distance markings are applied and calibrated should be described here, including a history of old methods.

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[image] WikiProject Metalworking: This article is part of Measuring tools and gauges.