{{Short description|Drafting instrument used to draw parallel lines}} {{use dmy dates|date=July 2021|cs1-dates=y}} [[File:Parallel-rule.jpg|thumb|Parallel rule in plastic with aluminum arms lying on a cutting mat]] '''Parallel rulers''' are a drafting instrument used by navigators to draw parallel lines on charts. The tool consists of two straightedges joined by two arms which allow them to move closer or further away while always remaining parallel to each other.
==History== The parallel ruler was invented at about 1584 by Fabrizio Mordente,{{fact|date=April 2023}} as well as by Taqi al-Din who died in 1585.<ref name=":02">{{Cite book|title=Biographical Encyclopedia of Astronomers|last=Fazlıoğlu|first=İhsan|date=2014|publisher=Springer, New York, NY|pages=2123–2126|language=en|doi=10.1007/978-1-4419-9917-7_1360|chapter = Taqī al-Dīn Abū Bakr Muḥammad ibn Zayn al-Dīn Maҁrūf al-Dimashqī al-Ḥanafī|isbn = 978-1-4419-9916-0}}</ref> However it was not in common use (at least in Europe) until the 18th century.<ref name="NMM_2009_1"/>
thumb|right|Captain Field's Improved Parallel Rule In the 19th century a retired sea captain, Captain William Andrew Field{{refn|Captain William Andrew Field (c. 1796–1871).<ref name="RootsWeb">[http://freepages.rootsweb.com/~heveningham/genealogy/page11.html Rootsweb, Captain Andrew Field]</ref> In February 1833 he rescued 14 sailors from the Sicilian brig Felicita, which was wrecked on rocks at the entrance to Sandy Haven in Milford Haven for which he received the RNLI Silver Medal and a medal from the Royal Humane Society.<ref name="RootsWeb"/>|group=Note}} improved the design by adding a protractor-style scale to the upper edge of one rule, and compass points to the opposing edge, which made reading bearings easier.<ref name="NMM_2009_1"/> Examples exist of boxwood, ivory or ebony, usually with brass hinges.<ref name="NMM_2009_1"/><ref name="NMM_2009_2"/> The instrument usually had two links, but longer models sometimes had three,<ref name="Riches_2009"/> and sometimes the links were scissored.<ref name="NMM_2009_3"/> Another variation is the "roller" model which included a cylindrical roller for ease of use.<ref name="Riches_2009"/>
==See also== * Cras protractor * Technical drawing tools
==Notes== {{reflist|group=Note}}
==References== <references>
<ref name="NMM_2009_1">{{cite web |title=Captain Field's Improved Parallel… (NAV0602) |date=2009 |work=Astronomical and navigational instruments |publisher=National Maritime Museum |url=http://www.nmm.ac.uk/collections/explore/object.cfm?ID=NAV0602 |access-date=2009-06-23 |url-status=dead |archive-url=https://web.archive.org/web/20110802022147/http://www.nmm.ac.uk/collections/explore/object.cfm?ID=NAV0602 |archive-date=2011-08-02}}</ref> <ref name="Riches_2009">{{cite web |url=http://www.mathsinstruments.me.uk/page39.html |title=Parallel rules: Rolling and bar types |author-first=D. M. |author-last=Riches |date=2009 |orig-date=2001 |work=Mathematical Instruments - A private collection |access-date=2009-06-23 |url-status=live |archive-url=https://web.archive.org/web/20210722202722/http://www.mathsinstruments.me.uk/page39.html |archive-date=2021-07-22}}</ref> <ref name="NMM_2009_2">{{cite web |title=Parallel rule (NAV0601) |date=2009 |publisher=National Maritime Museum |work=Astronomical and navigational instruments |url=http://www.nmm.ac.uk/collections/explore/object.cfm?ID=NAV0601 |access-date=2009-06-23 |url-status=dead |archive-url=https://web.archive.org/web/20110609021405/http://www.nmm.ac.uk/collections/explore/object.cfm?ID=NAV0601 |archive-date=2011-06-09}}</ref> <ref name="NMM_2009_3">{{cite web |title=Parallel rule (NAV0618) |date=2009 |publisher=National Maritime Museum |work=Astronomical and navigational instruments |url=http://www.nmm.ac.uk/collections/explore/object.cfm?ID=NAV0618 |access-date=2009-06-23 |url-status=dead |archive-url=https://web.archive.org/web/20110609021504/http://www.nmm.ac.uk/collections/explore/object.cfm?ID=NAV0618 |archive-date=2011-06-09}}</ref>
</references>
== External links == * [https://boatsafe.com/navigation/rules1.htm How to use parallel rulers]
Category:Navigational equipment
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