On 9/14/15 10:53 AM, John Yeung wrote:
I'm not enough of a typesetting geek to know the term "quad"
Fair enough. To "quad" a line of type is to insert spacing material on
either or both sides of the type, in order to fill out the line.
To "quad left" is to put the type on the left, and the extra spacing
material on the right.
To "quad right" is to put the type on the right, and the extra spacing
material on the left.
To "quad center" is to insert extra spacing material on both sides, to
center the type in the column.
To "justify" is to divide the extra space needed to fill the line among
the word spaces, as evenly as possible, so that the left and right
margins of the column are straight. The Linotype introduced the use of
the "spaceband," a variable-width piece of spacing material, that
allowed the extra space to be divided PRECISELY evenly.
The term "quad" comes from the basic unit of spacing material, the "Em
Quad." This is a square piece, with a set width equal to the point size.
Traditionally, a lowercase "m" has a set width of one Em. When setting
all caps, the ideal word space is half an Em, called an "En Quad," or
"Nut." When setting upper and lowercase, the ideal word space is a third
of an Em, called a 3-Em Space.