Catalogs normally contain a descriptive and dated (sometimes-coded) cover, a table of contents, index, illustrations, and then the meat of the catalog, the applications. The applications are normally arranged two ways: (l) alphabetically by vehicle name, and (2) numerically by part number. Jobbers may store their catalogs using the Weatherly filing system, a three-digit number on the front of the catalog, but this is of little interest to the do-it-yourselfer. What does interest you is the alphabetical listing of vehicles by make and model.
Many manufacturers print their parts catalogs every year, but some only print every two years and supply a supplement during the off year. It is essential to check the date of the catalog to be sure it has the latest information. Working with an outdated catalog is sometimes worse than working with no catalog at all.