Razor be used on both sides, with two open edges. The blade on the double-edged safety razor is slightly curved to allow for a smoother and cleaner shave. In 1901, the American inventor King Camp Gillette, with the assistance of William Nickerson, patented a new variation of safety razor with disposable blades. Gillette realized that a profit could be made by selling an inexpensive razor with disposable blades. This has been called the razor and blades business model, and has become a very common practice for a wide variety of products. Many other brands of safety razors have come and gone.
Safety razor Rockwell, ShaveCraft, Van der Hagen, Weishi and Wilkinson Sword, with several of them producing razors that are marketed under other brands. Often different models of razors within a brand share the same razor-head designs, differing primarily in the color, length, texture, material(s), and weight of the handles. Three-piece razors generally have interchangeable handles, and some companies specialize in manufacturing custom or high-end replacement handles. Variations in razor head designs include straight safety bar (SB), open comb (OC)(toothed) bar, adjustable razors, and slant bar razors. The slant bar was a common design in Germany in which the blade is slightly angled