The guideline describes the design and use of X-ray lenses, which are based on the refraction of X-rays. As the refractive index behaves different as in the optical range and takes values slightly less than one these lenses are constructed completely different as optical lenses. Depending on the manufacturing methods the guideline explains the design of lenses with point- or line-like focal spots and presents the basic information for calculations. Basic parameters are listed in detail.