double edge

A safety razor is a shaving implement with a protective device positioned between the edge of the blade and the skin. The initial purpose of these protective devices was to reduce the level of skill needed for injury-free shaving, thereby reducing the reliance on professional barbers.
Protective devices for razors have existed since at least the 1700s: a circa 1762 invention by French cutler Jean-Jacques Perret added a protective guard to a regular straight razor. The first known occurrence of the term "safety razor" is found in a patent from 1880 for a razor in the basic contemporary configuration with a handle in which a removable blade is placed (although this form predated the patent).Safety razors were popularized in the 1900s by King Camp Gillette's invention, the double-edge safety razor. While other safety razors of the time used blades that required stropping before use and after a time had to be honed by a cutler, Gillette's razor used a disposable blade with two sharpened edges. Gillette's invention became the predominant style of razor during and after the First World War, when the U.S. Army began issuing Gillette shaving kits to its servicemen.Since their introduction in the 1970s, cartridge razors and disposable razors – where the blades are embedded in plastic – have become the predominant types of safety razors.

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