Government documents are arranged using a different classification system from the rest of the library collection. Documents are arranged in the Superintendent of Documents (SuDoc) classification system rather than the Library of Congress (LC) Classification or the Dewey Decimal systems. 

The SuDocs classification system is based upon the government agency that produced the document.  This means that documents are grouped by their publishing agencies, not by the subject of the resource.

Government agencies can grow, divide, or change responsibilities over time. This means that the same type of document could be shelved in different places based upon the agency that published the document. For instance, the Department of Health and Human Services originated in 1980. Before that it was Department of Health, Education and Welfare dating from 1953.

Finding Government Documents on the Shelf with SuDocs
To find material on the shelf, use each element of the SuDocs number one at a time.
                        HE 20                . 4002:            B 74/3/                        998
                        (1)                    (2)                   (3)                    (4)

1. Documents are shelved in alphanumeric order; first alphabetically by the first letters of the SuDocs number.  The first letter(s) often signify the originating department of agency: A=Agriculture, C=Commerce, D=Defense, NAS=National Aeronautics and Space Administration
   
2. The period is not used as a decimal point, but rather to indicate the beginning of the next element of the SuDocs classification scheme.  Therefore, HE 20.5:ST 4 is located on the shelf before HE 20.4002:B 74/3/998, because 5 is less than 4002.
   
3. Letters come before numbers (HE 20.4002:B 74/3/998 before HE 20.4002:74).
   
4. For those documents published prior to 2000, when a year was used at the end of a SuDocs number (signifying an edition published in that year), the first digit was dropped, so 1992 became 992.  Dates are not filed in with other numbers.  Therefore, HE 20.4002:B 74/3/998  comes before HE 20.4002:B 74/3/18.
   

The examples below represent a shelf of U.S. Government Documents correctly arranged.
A 1.9:OP 7/973
                                A 1.9:OP 7/3
                                                        A 1.32/2:H 11
                                                                                      AA 1.9/3:84/1
                                                                                                                    C 3.2:M 58/984

SuDocs Tutorial from GODORT

SuDocs Tutorial