Edge index

This form of index consists of marks on the edges of the pages of a printed work. These marks are step-like printed and usually contain order words, letters or numbers, for example A to Z in a dictionary or telephone book. Usually they are coloured and help to find desired points, especially in reference works. They are “produced by means of printed rules that run to the edge of the sheet (bled) and can thus be seen on the fore edge of the closed book. Edge indexing has the advantage of being part of the printing process, and also allows the use of virtually unlimited headings, as well as adding nothing to the overall cost of binding. Its principal disadvantage is that the user does not know what the mark on the edge refers to while the book is closed.” When each edge index mark labels one chapter, the desired one can be found by counting the marks. When the edge index marks label first letters in a dictionary or telephone book, some can be identified by their “thickness”, i.e. in English there are only few words beginning with “Q” but a lot beginning with “S”.