It is also possible to print patterns of lines similar to those produced by ruling. Ruling, however, has several distinct advantages over printing, including: 1) the absence of glare. (Glare in this context refers to the effect produced when more light is reflected from the printed lines than the paper itself, and results in strain on the eye of the user. Ruled lines do not produce glare because the ruling inks are aqueous liquids, and their color, therefore, does not stem from insoluble pigments, but from dyes which are absorbed into the surface of the paper. Modern offset lithography appears capable of producing less glare than other printing methods, and today, certain kinds of ruled lines are now often produced by web offset printing. Loose-leaf books, checkbooks, and other mass produced items are today always printed); 2) the simplicity of multi-color work. (The ease with which various colors can be ruled side by side in one operation is also closely related to the nature of ruling inks. Essentially, ruling uses the same technique commonly known as SPLIT FOUNTAIN printing, in which the reservoir is compartmented, each section containing ink of a different color. Printing ink, on the other hand, is a highly viscous material that must pass through a series of rollers before it can be applied to the image carrier. Ruling ink is of low viscosity and can be fed to the ruling pens or discs by capillary action; therefore many different colors can be ruled extremely close to each other); and 3) writing done in ink will not skip as it may if the ruled lines are printed.
2. The ruling on the printed pages of letterpress books for the purpose of setting off the text from headlines, pagination, notes in the margins, etc. This type of ruling was prevalent from about the mid-16th century on the continent to the end of the 18th century in England. The color of the ruling is almost always red, now often faded to brown, particularly in the earlier continental books. The practice was usually reserved for large paper copies or special copies. Professional rulers were available for this work. (256 , 320 )