Pocket part - Wikipedia, the free encyclopedia. If you are an old lawyer, you remember pocket parts. I used to spend hours in the law library inserting the book updates into a pocket at the back of the book (hence the name), so that law publishers could make money. Nowadays, legal resources are kept current on a web server somewhere. No wonder law book publishers are struggling. Does anybody buy these things anymore? I haven't inserted a pocket part for many years; but, I wonder if they still exist? Anyone out there still keeping a paper library, and updating with paper pocket parts?