Thumbscrew Ridge is a type of knurling, which is a manufacturing process that creates a pattern of ridges on the surface of a material. The ridges are created by pressing a hardened tool against the material, which is then rotated to create the desired pattern. Thumbscrew Ridge is a specific type of knurling that is used to create a ridge pattern that resembles the shape of a thumbscrew. This type of knurling is often used in the production of screws and other fasteners, as well as for decorative purposes.