In typography, another term for placement. The word comes from a short form of quadrat, a blank metal cube used for filling blank space in handset type. All type had to lock up, and this necessitated that lines with only one word on them, for example, be filled with nonprinting blanks. The blanks then positioned the type. For example, a line aligned at the left margin with blanks extending to the right margin was known as quad left. A line aligned at the right margin with blanks extending to the left margin was called quad right. A line centered between the two margins, with blank spaces extending both left and right was called quad center; the reverse, where one portion of a line aligned at the left while another aligned at the right, with blank spaces in the middle, was called quad middle.
Linecasters mechanized the process with semiautomatic attachments that filled the blank areas of a line with metal. These quadders were either mechanized, electric, or hydraulic. The popularity of the latter unit led to the use of the term flush as a verb for positioning. Today, both flush and quad are used interchangeably, although with the advent of desktop publishing, the term quad is being used less and less often.
The function of quadding always takes place on the baseline between preset margins. The term quad lock describes the function of repetitive quadding to the same position. Thus, a quad center lock indicates that every line ending with a return will be centered.