The book is intended for radio amateurs interested in searching for various metal objects using special equipment, which primarily includes metal detectors. The corresponding sections provide schematic diagrams and drawings of printed circuit boards of both simple and more complex designs. Recommendations on self-manufacture and tuning of metal detectors, as well as tips on their practical use are given. This edition will be useful not only for trained radio amateurs, but also for all readers interested in this topic, since most of the presented designs can be made by both an adult and a student who has never held a soldering iron in their hands.