P.I. Orlov finalized and replenished the material of the first and second books, but did not manage to finish the third (last) book. The first book discusses the general principles of design based on unification and typification, the creation of derivative machines, ensuring development reserves in their design, increasing durability and reliability. The second book gives the basis for the design of cast and machined parts, plastic deformation joints, welded, riveted, key, spline joints, sliding and rolling supports, retaining rings and other parts. In the third book, fastening connections, methods of their locking, seals of movable and fixed connections of parts, compression springs, tension and torsion, pipeline connections, polymer products are considered; typical structural units of retainers, axle fasteners, spherical joints and other parts are described.