Areas of a page between the printed, written, or illustrative matter (text area) and the edges of the leaf. The four margins are usually called the 'head' (or top); 'fore-edge' (or outer, outside, side); 'tail' (or bottom foot); and 'inner' (or gutter).
Roberts, Matt, Don Etherington, and Margaret R. Brown. 1982. Bookbinding and the conservation of books: a dictionary of descriptive terminology. Washington: Library of Congress.