Johannes Gutenberg (2/8): The art of manual typesetting

Johannes Gutenberg arranged each unit of metallic type along a composing stick. The total length of each line could be adjusted, or "justified", in relation to that of every other line. In order to ensure that several lines of composed metallic type formed a neat block, with straight left and right edges, it was first of all necessary to introduce some slight variation into the spaces between the letters within each word and finally to vary the size of the space between the words. If necessary, blind material was added.