Details of a planar X-ray waveguide (PXW) built using total X-ray reflection phenomenon are described. The design of the planar X-ray waveguide-monochromator is mentioned in passing. The efficiency of the X-ray beam forming systems based on a planar X-ray waveguide and on a conventional slits superimposition is compared. Characteristics of an X-ray diffractometer equipped with PXW are analyzed. Experimental diffractometer patterns of a polycrystal thin gold film on a Si wafer obtained by using a HZG-4 diffractometer equipped with PXW in the modified Bragg-Brentano diffraction geometry are presented.