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 greatly extend their life. Disposable safety razors can be sharpened using various methods. There are commercial devices intended for this duty (Razormate, RazorPit, Blade Buddy, etc.). Myths claim that it is possible to sharpen a disposable razor by utilizing a pyramid but this is pseudoscience. Double-edge (DE) safety razors remain a popular alternative to proprietary cartridge razors, and usually offer significantly lower total cost of ownership since they are not marketed under the "razor and blades business model". DE razors are still designed and produced in many countries. Better known manufacturers include Edwin Jagger, Feather, iKon, Lord, Merkur, Mühle, Parker,