This document provides background information on a practical guide to free-energy devices. It discusses the author's interest in free-energy which began with a 1980s UK television program. It notes the lack of specific, practical information available on free-energy systems at the time. The author then wrote the first edition of this guide in 2005 to share what he had learned from his research in order to help others. The guide is intended as an introduction to the subject and covers various free-energy devices and inventors, but is not a complete resource. It aims to provide concise descriptions of devices and how they operate rather than extensive mathematical analysis.