letter

In letterpress printing, a letter is a single piece of metal type, cast as a right-reading mirror image in reverse relief, that prints one character. The face of the type bears the raised image of a letter, numeral, or punctuation mark; the body, or shank, is the rectangular block of metal (typically a lead-tin-copper alloy) that carries this face and determines its height and width. When locked together in a chase with other letters, spaces, and quads, letters form the text that will be inked and printed.

The height of a letter from foot to face is standardized at roughly 0.918 inches in Anglo-American printing, known as type height. The width of the body varies with the character: an m is much wider than an i. Before digital typesetting, a printer's working capital was tied up in thousands of sorts, or individual letters of each typeface and size needed for the job at hand. A complete assortment of sorts in a given typeface and size is called a font.

The term letter in this sense is dated because hot metal composition has been almost entirely displaced by phototypesetting and digital imaging. Nonetheless, the vocabulary persists in foundry work and among restorers and historians of printing. The name derives simply from the fact that each piece of type carried the image of a letter of the alphabet, distinguishing it from spacing materials and decorative sorts.

Casting defects in letters are common: shrinkage voids, rough faces, fins along the side seams, and improper height-to-paper surface cause makeready problems and uneven impression. Worn letters show sharpness loss in the face and lose crispness in the printed impression. Badly worn or damaged letters are sorted out and either melted back or discarded. A printer working at speed must keep sufficient duplicate letters on hand to avoid constant searching through the case, particularly for common sorts like e, t, and a.