Ruler

A ruler, sometimes called a rule, scale or a line gauge or metre/meter stick, is an instrument used to make length measurements, whereby a length is read from a series of markings called "rules" along an edge of the device.

In geometry, straight lines between points may be drawn using a straightedge (ruler without any markings on it).

[3] In the late 18th century the metric system came into use and has been adopted to varying degrees in almost all countries in the world.

The oldest preserved measuring rod is a copper-alloy bar that dates from c. 2650 BC and was found by the German Assyriologist Eckhard Unger while excavating at the Sumerian city of Nippur (present-day Iraq).

Rulers made of ivory were in use by the Indus Valley civilization period prior to 1500 BC.

[7] Ludwig Wittgenstein famously used rulers as an example in his discussion of language games in the Philosophical Investigations (1953).