A student asked how to look up a legal topic using a West Key Number and I realized I didn't know how! I found this great, simple explanation of the West Key Number System and how to understand/use it. West Key Number System
If you're not familiar with it already, you'll recognize a key number by the little symbol of a key that appears before a number.
There's also a Wikipedia entry about the West American Digest System, which is what the Topic and Key Numbers refer to.