The book is a monograph written on the results of the author's work. It investigates the diffraction of flat electromagnetic waves on perfectly conductive bodies, the surface of which has fractures. The linear dimensions of the bodies are assumed to be large compared to the wavelength. The method developed in the book takes into account the perturbation of the field near the fracture of the surface and allows to significantly clarify the approximations of geometric and physical optics. Expressions found for the scattered field in the far zone. A numerical calculation of scattering characteristics has been performed and their comparison with the results of a strict theory and with an experiment. The book is intended for physicists and radio engineers interested in diffraction phenomena, as well as for undergraduate and graduate students specializing in antennas and radio wave propagation.