A metallic male snap part is capable of enhancing coupling strength with a female snap part by giving appropriate and sufficient elastic deformability to the projection of the male snap part which can be coupled to a depression of the female snap part. The distance between the object surface and the radiometer is measured by a rangefinder, controlled by the radiometer. Both \u201ch\u201d-shaped and \u201cH\u201d-shaped versions are provided.