US Patent 11278467 Stretching tool

A stretching tool includes: two spheres of identical size, each with a two-layer structure consisting of an inner shell and an elastic outer covering layer which is affixed to the surface of the inner shell and which has a hardness relatively less than that of the inner shell; and a connecting section that connects the inner shells of the two spheres so that an extended axial center line passes through the centers thereof. The spheres' exterior surfaces have ridges that have saw-blade-shaped cross-sections and extend over the extended axial center line continuously from an end section on the outermost side of each of the two spheres toward the connecting section.