Trade custom gives the name spaces to the small type blanks and quads to the larger type blanks. These are further specified according to their thickness or fractional part of the em, or square, as 3-to-em, 4-to-em, 5-to-em (hereafter in this treatise, for convenience, termed respectively the 3-space, 4-space, 5-space). Very thin blanks are hair spaces or justifiers. The en quad (half the square) is sometimes called the thick space. 2 The large blanks are the em quad 2-em quad, and (for types of 12-point and smaller) 3-em quad.

To the beginner the difference between some spaces and quads is not always clear because of the frequent identity of size in different type bodies. Thus, a 3-space of an 18-point font is 18×6 points, which is the same as a 3-em quad of 6-point. The difference between the two is in the position of the nicks (except where spaces and quads are cast without nicks). On the 6-point quad the nick is along the 3-em side, while on the 18-point space it is across the narrow 6-point edge. The identity in size is often a convenience, when quads or spaces of one size are exhausted, by allowing the use of pieces from another font.

The apprentice should become familiar with these regular spaces of his case at the outset. He may learn to distinguish them by putting one of each thickness side by side frequently for comparison. By doing this with each size of type as he comes to use it he will soon learn to distinguish the spaces at a glance, to select quickly the space he wants, and to sort them properly in distributing.

These four regular thickness of spaces meet most of the requirements of type composition. Besides their own individual widths they may be combined into any other widths for spacing and justifying lines. The following table, showing twenty-four different widths less than the em which can be made with the four original spaces, should be studied by the beginner who is in despair because he cannot find just the right thickness to fit his line.

2 Note. The 3-space is often miscalled the thick space; but as it is commonly known as the normal space (i.e. neither thick nor thin) it seems illogical to call it also a thick space. The en quad or any space thicker than the 3-space is obviously a thick space.