Library and Archives Service
Once you have found your item listed on Library Search, you need to note which library stocks the item (Main, Deiniol, Normal, Welsh, Maelor etc.). The location should tell you which library stocks the item and in which section within that library it will be located (pamphlet, large book, journal etc.).
The books are kept in Library of Congress classification order. The call numbers begin with a letter and run alphabetically with each broad subject grouping allocated its own letter. The letter and number that follow the first letter narrow down the subject.
Please see this video that explains how to find items in the library.