A ruler, generally known as a rule or line gauge, could be a device employed in pure mathematics and technical drawing, similarly because of the engineering and construction industries, to live or draw straight lines.

Rulers have long been made up of totally different materials and in multiple sizes. Some area unit wood. Plastics have conjointly been used since they were invented; they'll be shaped with length markings rather than being scribed. Metal is employed for a lot of sturdy rulers to be used within the workshop; generally, a metal edge is embedded into a wood table ruler to preserve the sting once used for straight-line cutting. twelve in or thirty cm long is helpful for a ruler to be unbroken on a table to assist in the drawing. Shorter ruler's area unit was convenient for keeping in a very pocket. Longer rulers, e.g., eighteen in (46 cm) area unit necessary in some cases. Rigid wood or plastic yardsticks, one yard long, and meter sticks, one meter long, are used. Classically, long measure rods were used for larger comes, currently outmoded by tape, surveyor's wheel or optical maser rangefinders.

Desk rulers area unit used for 3 main purposes: to live, to assist in drawing straight lines and as a straight guide for cutting and grading with a blade. sensible rulers have distance markings on their edges.

A line gauge could be a kind of ruler employed in the printing trade. These are also made up of a spread of materials, usually metal or clear plastic. Units of activity on a basic line gauge sometimes embrace inches, agate, picas, and points. a lot of elaborated line gauges could contain sample widths of lines, samples of a common kind in many purpose sizes, etc.

Measuring instruments similar in performing to rulers area unit created moveable by folding (carpenter's folding rule) or retracting into a coil (metal tape measure) once not in use. once extended to be used, they're straight, sort of a ruler. The illustrations on this page show a two m (6 linear unit seven in) rule, that folds down to a length of twenty-five cm (10 in) to simply slot in a pocket, and a five m (16 ft) tape, that retracts into a little housing.

A flexible length measuring system that isn't essentially straight in use is that the tailor's material tape, a length of tape mark in inches and centimeters. it's wont to live around a solid body, e.g., a human waist activity, similarly as the linear activity, e.g., inside leg. it's rolled up once not in use, taking over a very little area.

A contraction rule is formed having larger divisions than commonplace measures to permit for shrinkage of a metal casting. they will even be referred to as a shrinkage or shrink rule.

A ruler package program is often wont to live pixels on a visual display unit or portable. These programs are referred to as screen rulers.

In pure mathematics, a ruler with no marks thereon (a straightedge) is also used just for drawing straight lines between points. A hand tool is additionally wont to facilitate draw correct graphs and tables.

A ruler associated compass construction refers to construction mistreatment an unmarked ruler and a compass. it's the potential to cut an associate angle into 2 equal components with ruler and compass. It is often established, though, that it's not possible to divide associate angle into 3 equal components mistreatment solely a compass and hand tool — the matter of angle trisection. However, ought to 2 marks be allowed on the ruler, the matter becomes soluble.

A wood rule and different tools found on board the sixteenth-century carack mother Rose

In the history of activity, several distance units are used that were supported anatomy components like the linear unit, hand, and foot, and these units varied long by era and site. within the late eighteenth century, the system of weights and measures came into use and has been adopted to varying degrees in the majority of countries within the world. The oldest preserved measuring device could be a copper-alloy bar that dates from c. 2650 BCE and was found by the German Assyriologist Eckhard Unger whereas excavating at Nippur. Rulers manufactured from Ivory were in use by the Indus vale Civilization amount before 1500 BCE. Excavations at Lothal (2400 BCE) have yielded one such ruler mark to concerning 1⁄16 in. (1.6 mm) Ian Whitelaw holds that the Mohenjo-Daro ruler is split into units such as one.32 inches (33.5 mm) and this area unit marked come in decimal subdivisions with superb accuracy, to inside zero.005 inches (0.13 mm). Ancient bricks found throughout the region have dimensions that correspond to those units.

Anton Ullrich unreal the folding ruler in 1851. Frank Hunt later created the versatile ruler in 1902.

The equivalent of a ruler for drawing or reproducing a sleek curve, wherever it takes the shape of a rigid example, is understood as a French curve. a versatile device which might be bent to the required form is understood as a flat spline, or (in its a lot of trendy incarnation) a versatile curve. traditionally, a versatile lead rule utilized by masons that would be bent to the curves of molding was referred to as a lesbian rule.