Cutter:

The Cutter number, or Cutter, is an alpha-numeric device for representing words or names by using one or more letters followed by one or more arabic numerals treated as decimal numbers. The combination of letters and numbers, called the Cutter, follows the LC classification number and is preceded by a decimal point. It is named for Charles Ammi Cutter, who developed several tables using letters and numbers to achieve an alphabetical arrangement. The Cutter enables alphabetic order to be maintained within a given class. Book numbers and some subdivisions in the classification schedules are types of Cutter numbers.

Where double Cuttering is used, the second Cutter is sometimes known as the book or author number/Cutter, while the first is alternately the subject or class Cutter or, in the case of literature, the author Cutter.

Example:

Call number: Z733.U58G66 1991

Cutter number: .U58 [for the United States]

G66 [for the author]