Short metal spaces and quads (from quadrat, a square), used for blanks between words and elsewhere, are of various thicknesses, as illustrated below. An em is a square of type body of any size. This 10-point em □ is ten points square; a 10-point three-to-em space is one third of the em, a four-to-em is one fourth, etc. The en quad is really a thick space, though called a quad, and is equal to half the em. Larger blanks are the two-em and three-em quads, used to fill the last lines of paragraphs and other wide spaces.
The metal blanks shown here are the regular spaces and quads belonging to a font of type of the size of 10-point. They enable the compositor to obtain the many different spacings required to make lines the required length, and to properly separate words and place them wherever desired in the line. While these thicknesses of spaces are the usual kinds for sizes of type up to 12-point, larger types may have other kinds of spaces, six-to-em, eight-to-em, and even smaller divisions. The thickness of the hair space does not always bear the same proportion to the em quad; in some sizes it is one sixth of the em, in others it may be one eighth or one twelfth. Very thin spaces (copper ½-point, brass 1-point), for exact spacing and justifying, are supplied by dealers.
A space of the thickness intermediate between the three-to-em and the en quad, known as a patent space, has been made for use in book work. Although it has great advantage as a substitute for two of the thinner spaces when these are needed in spacing a line, its use has been limited and it is not included with the usual assortment furnished by dealers.
The common spaces and quads for general work, when the type itself is used for printing, are about seven-eighths of the height of the type, so that they are well below the printing surface. A type-page composed with these spaces will have a little deep hole at the top of each space. These numerous little holes present a difficult surface for making a good wax mold when an electroplate is made for printing. Where much molding is to be done, higher spaces, quads, and other blanks are provided. These high spaces and quads reach nearly to the shoulder of the type.
How Type is Made
The mold in which type is cast consists of two essential parts—the steel box in which the body is formed, and the matrix which contains a sunken image of the character. The matrix covers the opening at one end of the mold, and on the opposite end (which is the foot of the type) is an opening through which the melted metal is injected. A mold is made for a single body-size of type but it is adjustable sideways to correspond to the various widths of the letters in an alphabet. One mold may be used to cast, in succession, all the letters of a font of type, or it may be used to cast any number of fonts of different faces that may be made on the same body, by merely changing the matrices that form the face. The mold is made in two sections, which are fitted together so as to close up to the required width of the letter, and, after the cast is made, to open slightly in order to release the type.