[[File:Linotype matrix Casting Edge.jpg|thumb|Duplexed Linotype matrix for regular and bold styles.]]
A '''duplexed''' letter has the same width between its bold and light (non-bold) styles<ref>{{cite book|last=Durbeck|first=Robert|title=Output Hardcopy Devices|url=https://books.google.com/books?id=s329hWFOqPUC&pg=PA502|year=2012|publisher=Elsevier|isbn=978-0-323-14674-6|page=502|quote= the fitting of letter shapes to certain available widths, “duplexing”, or the placing of a light and bold character on the same width}}</ref> or between its italic and non-italic styles.<ref>{{cite book|last=Byers|first=Steve|title=The Electronic Type Catalog|url=https://books.google.com/books?id=rztUAAAAMAAJ|year=1991|publisher=Bantam Books|isbn=978-0-553-35446-1|page=11|quote= both designs had to measure the same width. This was called duplexing. If an italic was to be paired, or duplexed, with a roman, the italic was redrawn and refitted to the width of the roman.}}</ref>
A '''duplexed''' matrix with two sites for casting letters was common on Linotype machines. By switching the position of the matrix two styles could be cast, which would have identical width.<ref>{{cite book|last=Durbeck|first=Robert|title=Output Hardcopy Devices|url=https://books.google.com/books?id=s329hWFOqPUC&pg=PA502|year=2012|publisher=Elsevier|isbn=978-0-323-14674-6|page=502|quote= the fitting of letter shapes to certain available widths, “duplexing”, or the placing of a light and bold character on the same width}}</ref><ref>{{cite book|last=Byers|first=Steve|title=The termElectronic hasType itsCatalog|url=https://books.google.com/books?id=rztUAAAAMAAJ|year=1991|publisher=Bantam originBooks|isbn=978-0-553-35446-1|page=11|quote= inboth matricesdesigns had to measure the same width. This was called duplexing. If an italic was to be paired, whereor duplexed, characterswith coulda shareroman, matricesthe italic was redrawn and refitted to the width of the roman.}}</ref><ref>{{cite web |title=duplexing, cross-rail duplexing |url=https://www.fonts.com/content/learning/fontology/glossary/d |website=Fonts.com |quote=A metal-type term referring to {{linktext|linecasting}} characters created to share matrices (the pieces of metal in which characters were cast) that consequently were designed to have exactly the same character widths (set widths). Typically, a roman typeface and its corresponding italic or a roman and a bold from the same typeface family might be designed to cross-rail duplex. When emulating typeface designs created for linecasting equipment, type designers need to be aware that the duplexing in these faces sometimes resulted in less than ideal spacing and/or character proportions in one or more of the typefaces that were duplexed.}}</ref> A common combination was regular and italic for text faces, or regular and bold as on [[Metro (typeface)|Metro]], but Linotype also offered more unusual combinations, such as a serif text face duplexed with a bold sans-serif for emphasis.<ref name="Handbuch der Schriftarten">{{cite book|title=Handbuch der Schriftarten|date=1926|pages=181–218|publisher=Seemann|location=Leipzig|p=293|url=http://www.klingspor-museum.de/Handbuch-der-Schriftarten.html|accessdate=30 June 2017}}</ref>