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parallel rulers

plural noun
  1. a pair of straightedges connected by two pivoted crosspieces of equal length so as to be parallel at all times, used for various navigational purposes, especially for transferring the bearing of a plotted course to a compass rose.
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Origin of parallel rulers

First recorded in 1695–1705
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for parallel ruler

parallel ruler

noun
  1. engineering a drawing instrument in which two parallel edges are connected so that they remain parallel, although the distance between them can be varied
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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012