Examples of headline letter spacing In typography, letter spacing, character spacing or tracking is an optically consistent adjustment to the space between letters to change the visual density of a line or block of text. Letter spacing is distinct from kerning, which adjusts the spacing of particular pairs of adjacent characters such as "7." which would appear to be badly spaced if left unadjusted. History Historically, with metal type, a kern meant having a letter stick out beyond the metal slug to which it was attached, or having part of the body of the slug cut off to allow letters to overlap. A kern could therefore only bring letters closer together (negative spacing). Digital kerning could go in either direction. Tracking can similarly go in either direction, but with metal type, one could make groups of letters only farther apart (positive spacing). In the days of hot metal typesetting, letter spacing required adding horizontal space between letters of words set in metal type in increments of a minimum of a half-point. Some publishers and typesetters avoided letter spacing because it was costly in materials and labor. Letter spacing required hand insertion of copper (a half-point), brass (one point), and printer's "lead" (two points) spaces between individual pieces of type or between matrices. Despite the cost, letter spacing was used in print advertising and book publishing. It was also used for very short phrases set in capital letters or small caps to prevent the phrases from appearing too black compared to the rest of the page. Printer and type designer Frederic Goudy stated that "Men who would letterspace blackletter would shag sheep." Goudy's statement inspired the title of the book Stop Stealing Sheep, an introduction to typography. Digital systems Word processing and desktop publishing programs for personal computers, such as LibreOffice Writer, Microsoft Word, Microsoft Publisher, WordPerfect, QuarkXPress, Adobe InDesign, Adobe FrameMaker, Adobe Illustrator, and Adobe Photoshop, use differing methods of adjusting letter spacing. Most systems have the default letter spacing at zero and instead use the character widths and kerning information built into the font itself. Although digital type sets tighter than metal type on average, this results primarily from the availability of kerning. Digital type does allow for negative sidebearings, which were uncommon in metal type because of the difficulty in cutting a "kern". In the days of machine-implemented lead typesetting, such as Linotype machines and the Monotype System,