Ruler 65593 221697574 2008-06-25T17:56:40Z 16@r 839108 {{dablink}} {{dablink|This article is about the drawing and measuring instrument. For the person who rules a country, see [[Monarch]] or [[Lists of incumbents]].}} [[Image:Lineale.jpg|thumb|right|180px|A variety of rulers]] [[Image:CarpentersRule.png|thumb|right|180px|A 2 metre carpenter's rule]] [[Image:TapeMeasure.png|thumb|right|180px|Retractable flexible rule]] [[image:Steel_ruler_closeup.jpg|thumb|180px|A closeup of a steel ruler]] A '''ruler''', or '''rule''', is an [[Measuring instrument|instrument]] used in [[geometry]], [[technical drawing]] and engineering/building to measure distances and/or to rule straight lines. Strictly speaking, the ''ruler'' is essentially a [[straightedge]] used to '''rule''' lines and the calibrated instrument used for determining measurement is called a 'measure'. However, common usage is that a ruler is a calibrated straightedge that can be used for making measurements. ==Types== A Rule has the measurements start from the end, whereas a ruler has a gap between the end and the measurements. Rulers have long been made of wood in a wide range of sizes. [[Plastics]] have been used since they were invented; they can be moulded with length markings instead of being [[scribed]]. Metal is used for more durable rulers for use in the workshop; sometimes a metal edge is embedded into a wooden desk ruler to preserve the edge when used for straight-line cutting. 12 inches or 30cm in length is useful for a ruler to be kept on a desk to help in drawing. Shorter rulers are convenient for keeping in a pocket. Longer rulers, e.g., 18 inches (45cm) are necessary in some cases. Rigid wooden or plastic [[yardstick]]s, 1 yard long and metre sticks, 1 metre long, are also used. Desk rulers are used for three main purposes: to measure, to aid in drawing straight lines and as a straight guide for cutting and scoring with a blade. 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.'' --> Measuring instruments similar in function to rulers are made portable by folding (carpenter's folding rule) or retracting into a coil (metal [[tape measure]]) when not in use. When extended for use they are straight, like a ruler. The illustrations on this page show a 2 [[metre]] carpenter's rule which folds down to a length of 24 [[centimetres]] to easily fit in a pocket, and a 5 metre long tape which retracts into a small housing. A flexible length measuring instrument which is not necessarily straight in use is the tailor's fabric [[tape measure]], a length of tape calibrated in inches and centimetres. It is used to measure around a solid body, e.g., a person's [[waist]] measurement, as well as linear measurement, e.g., inside leg. It is rolled up when not in use, taking up little space. == Ruler applications in geometry== {{main|Compass and straightedge}} In geometry, a ruler usually refers to an unmarked ruler (a[[straightedge]]), only used for drawing straight lines between points, not measuring. A [[compass and straightedge|ruler and compass construction]] refers to constructions using an unmarked ruler and a compass. It is possible to bisect and angle into 2 equal parts with ruler and compass. It can be proved, though, that it is impossible to divide an angle into 3 equal parts using only a compass and straightedge&mdash;the problem of [[angle trisection]]. However, should a single mark be allowed on the ruler, the problem becomes solvable. ==In heraldry== *The ruler (calibrated, though numbers are not shown) appears as a [[charge (heraldry)|charge]] in [[heraldry]], notably in the arms of [[Odouze]]. *The [[Freemason]]s are identified by a [[compass]] and [[Square and compasses|square]] device, the latter another type of ruler. Together, the tools represent judgement and discernment. ==See also== {{Wiktionary}} {{commonscat|Length measuring devices}} <div class= style="-moz-column-count:2; column-count:2;"> * [[Anton Ullrich]] (1825 -1895) [[Folding ruler]] inventor * [[Golomb ruler]] * [[Measuring rod]] * [[Perfect ruler]] * [[Rulering (punishment)]] * Scale rulers: [[architect's scale]] and [[engineer's scale]]. * [[Slide rule]] * [[Geometry template]] * [[Dividing engine]] * Erin Howell * [[Online ruler]] </div> {{Metalworking - Measuring tools and gauges}} [[Category: Dimensional instruments]] [[Category: Metalworking measuring instruments]] [[Category:Woodworking measuring instruments]] [[Category:Stonemasonary tools]] [[ar:مسطرة]] [[ca:Regle]] [[cs:Pravítko]] [[da:Lineal]] [[de:Lineal]] [[es:Regla graduada]] [[ko:자 (도구)]] [[id:Penggaris]] [[it:Riga (strumento)]] [[he:סרגל]] [[lt:Liniuotė]] [[nl:Liniaal]] [[ja:定規]] [[no:Linjal]] [[nds:Lienholt]] [[pl:Linijka]] [[pt:Régua]] [[ru:Линейка]] [[simple:Ruler]] [[sr:Лењир]] [[tr:Cetvel]] [[fi:Viivain]] [[sv:Linjal]] [[th:ไม้บรรทัด]] [[zh:尺子]]