justification

…held in the hand; (3) justifying the line; that is to say, spacing the letters in each line out to a uniform length by using little blank pieces of lead between words; and (4), after printing, distributing the type, letter by letter, back in the compartments of the typecase.

…the composing stick at the justification; that is, at the length of the line to be composed. Against the inside edge of the stick he places a lead, a strip of nonprinting lead alloy that later enables him, using a second lead, to grip the finished line in order to…