Tooling, or stamping, is the process of indenting materials (most often leather) with a heated tool. The tool can be anything, from a simple brass rod to an elaborate handle letter or fillet. A tooled impression may be filled with metal, darkened, or a simple indentation in the surface of the leather.
Although tooling is generally performed on leather, it can also be used to decorate any compressible material. Vellum is suitable for both blind and gold tooling. Most fabrics and papers will gold tool well, but should not be blind tooled. (Queen Elizabeth I had her entire library bound in gold tooled velvet, a most spectacular sight by all accounts.)
Tooling is used in a variety of crafts. Saddle and belt makers often blind tool their work. The monogrammed initials often available for luggage are a form of tooling. And bookbinders have used blind and gold tooling to decorate their covers for centuries.