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.
Straight razor called the "belly", and the area between the ridge and the cutting edge which is more hollow i.e. with a smaller radius of curvature. These two beveled areas have different curvatures and in a well-made razor they transition seamlessly in the ridge (belly) and the cutting edge respectively. Sometimes there are three bevels. The ridge stabilizes the blade against torsional flexing in a direction perpendicular to its longitudinal axis by acting as a lengthwise spine for the blade. The distance between the ridge and the back of the blade is inversely proportional to the hollowness of the blade and is