Most items in the library are shelved by Library of Congress (LC) call numbers. 

As an example, here's the call number for the book No logo: taking aim at the brand bullies by Naomi Klein:

HD2755.5.K575

How to Read LC Call Numbers

Locating an item on the shelf can sometimes be tricky because of how LC call numbers are filed. Keep the following in mind and you should have no problems. If you do, ask for help at the Library Services Desk - we're happy to assist.

1. The initial letter(s) file in alphabetic order:

H   HA   HB   HC   HD   J   JA   JC

2. The first numbers (before the next letter) are treated as a whole number with decimal, not as individual numbers. These then file in numerical order:

Correct: HD500.61   HD2755.12   HD2755.5   HD2755.65    HD2755.7
Incorrect: HD2755.5   HD2755.7   HD2755.12    HD2755.65   HD500.61

3. The letter following the decimal point files in alphabetical order.

4. The final numbers following the final letter are treated as a decimal, not as a whole number (yes, this is weird):

Correct: HD2755.5.K50   HD2755.5.K57   HD2755.5.K575    HD2755.5.K58
Incorrect: HD2755.5.K50   HD2755.5.K57   HD2755.5.K58   HD2755.5.K575

Structure of LC Call Numbers

Divisions and Subdivisions

The first letter of a call number represents one of the 21 major divisions of the Library of Congress system. In our example, 'H' stands for "Social Sciences".

The second letter, if present, represents a subdivision. In our example, "D" is for "Industry, Labour, & Land Use".

Books that are given the single letter are usually of a general nature for that subject area.  For example, the call number for the book Action and interpretation: studies in the philosophy of the social sciences is H61.A39.

Subject

The first set of numbers in a call number help to define the item's subject.

In our example, '2755.5' falls in the range of HD2709-HD2930.7 which deals with "Corporations".

Cutter Number

The final letter/number combination after the last decimal point is called the "Cutter Number". It usually reflects the name of the author.

In our example, the author's last name is Klein so the cutter number begins with 'K'.

The actual numbers after this letter are assigned so that all books with a given call number file in alphabetical order by author.