parallel rulers
Illustration — 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.
parallel rulers
Clipper · CC BY-SA 3.0
- Field
- navigational instrument · ruler
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Illustration — 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.
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wikidata · Q2051620 · wikipedia · Parallel rulers
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History
History
The parallel ruler was invented at about 1584 by Fabrizio Mordente, as well as by Taqi al-Din who died in 1585. However it was not in common use (at least in Europe) until the 18th century. • Illustration — Captain Field's Improved Parallel Rule In the 19th century a retired sea captain, Captain William Andrew Field 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. Examples exist of boxwood, ivory or ebony, usually with brass hinges. The instrument usually had two links, but longer models sometimes had three, and sometimes the links were scissored. Another variation is the "roller" model which included a cylindrical roller for ease of use.

Captain Field's Improved Parallel Rule, design c. 1854. Date for this model probably late 19th/early 20th century.
Rodhullandemu
Chart BA 4022 with parallel ruler and divider
BoH
Chronology
Dated record
Chronology
The full dated record · 2 entries
1584
parallel rulers first recorded.
1584
parallel rulers began in 1584.
Primary material
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reference work
- “Parallel rulers”, English Wikipedia, consulted as further reading
Reputable secondary · Wikipedia
authority record
- Wikidata, structured authority record Q2051620: parallel rulers
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The Encyclopedia exists whether or not anything is for sale. Corrections are recorded rather than overwritten, and every version of this record is kept. Published 14 August 2026.
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