What are screws and nuts?

Screws: is also composed of two parts of the head and rod of a class of fasteners, according to the use can be divided into three categories: machine screws, set screws and special purpose screws.

Nut: with internally threaded holes, the shape is generally shown as a flat hexagonal column, there are flat square or flat cylindrical, with bolts, studs or machine screws, used to fasten the connection between the two parts, so that it becomes a whole piece of work.