About Haynes Manuals Using a Haynes manual is like having a mechanic in every book. Haynes has teams of mechanics and writers who work together on each project vehicle to arrive at the best possible procedures for the home mechanic and then photograph the actual work and write instructions so the reader can easily follow along. Haynes manuals include procedures for everything from routine maintenance to complete engine overhaul, and include wiring diagrams in the back of each book.