: a printer's ruler on which measurements have been marked in picas, usually in other point sizes, and sometimes in inches
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a printer's ruler, usually marked off in points, picas, agates, and inches, and sometimes also in centimeters.
[1945-50]
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line gauge,
a printer's ruler, usually divided into picas and nonpareils on one edge and inches on the other.
Useful english dictionary. 2012.