Thumb index

Not to be confused with edge index.

A thumb index, also called a cut-in index^[1] or an index notch,^[2] is a round cut-out in the pages of dictionaries, encyclopedias, Bibles and other large religious books, and various sectioned, often alphabetic, reference works, used to locate entries starting at a particular letter or section. The individual notches are called thumb cuts and enable the reader to turn to any section they want.

A dictionary with thumb indexes (on the right).

Several ways to achieve this indexing effect were invented and patented in the 1970s by Arthur S. Friedman, a printing engineer in New York.^[3] Charles Halbert Denison also patented the marginal thumb indexing system for bookkeeping,^[4] with his business taken over by his wife Dimies T. Stocking Denison after his death in 1911.^[5][6]

See also

• Index (publishing)