A full measure is the distance from the leading edge of one line of text to the leading edge of the next line of text. It is also called a leading, or line spacing. The term is most often used in reference to typewriters, typesetting, and word processing.
The full measure of a typewriter is the distance from the platen to the carriage return. The platen is the cylindrical steel roller on which the paper is fed. The carriage return is the mechanism that moves the carriage back to the left margin. The full measure of a typesetting machine is the distance from the baseline of one line of type to the baseline of the next line of type. The baseline is the imaginary line on which the letters “sit.”
In word processing, the full measure is the distance from the top of one line of text to the top of the next line of text. This is also called the leading.
The standard full measure for typewriters, typesetting machines, and word processors is 12 points. This means that there are 12 points (1/6 of an inch) of space between the lines of text. Some word processors allow the user to change the full measure. For example, Microsoft Word has a “Line Spacing” tool that allows the user to set the full measure to single (1.0), 1.5, double (2.0), or triple (3.0) spacing.
The full measure is important because it affects the readability of the text. If the lines of text are too close together, the text will appear to be one block of text and will be difficult to read. If the lines of text are too far apart, the text will appear to be scattered on the page and will also be difficult to read. The standard full measure of 12 points is considered to be the most readable.