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.