Abstract: A column marker (10) to be used for marking columns on a book layout sheet (42) comprises an elongated ruler member (12) defining a straightedge (14) and a display surface (16) having unique column-marking indicia thereon. The unique column-marking indicia includes a plurality of sets (18A-G) of three side-to-side adjacent elongated bars (20A, 22A; and 24A; 20R; 22B, and 24B, etc.). The bars are parallel to the straightedge and many of the bars in each set are longer than other bars in the set. The longer bars are positioned further from the straightedge than the shorter bars. First ends (26) of the bars are aligned, while perpendicular tails (28 and 30) at second ends of the longer bars extend to the straightedge beyond ends of the shorter bars (32A-32G).