The Key is laid out as a standard index, with major categories and subcategories, allowing you to translate what you see in a cameo from words into possible identifications and/or symbolism. If you cannot find a specific entry in the alphabetical table, for example, DOG, try looking under a more generic term, in this case, ANIMALS, and its subcategories Dog and Hound. The categories ANGELS, ANIMALS, BIRDS and CHARIOTS are particularly dense with subcategories.
The Profiles can then be consulted for examples and more complete information.