A bad knife cuts one’s finger instead of the stick. (Portuguese) A dull knife cannot sharpen itself. (Korean) A good knife is not used for scraping. (Chinese) A knife cannot carve its own handle. (Korean) One knife keeps another in its sheath....

A knife is a hand held sharp-edged instrument consisting of handle attached to a blade used for cutting. The knife is a tool that can be used as a weapon. Its origins date as far back as two-and-a-half million years ago, as evidenced by the Oldowan...