 thumb|right|220px|a few paper clips of different colors. a paper clip (or sometimes paperclip) is an instrument used to hold sheets of paper together, usually made of steel wire bent to a looped shape. most paper clips are variations of the gem type introduced in the 1890s or earlier, characterized by the almost two full loops made by the wire. common to paper clips proper is their utilization of torsion and elasticity in the wire, and friction between wire and paper. when a moderate number of sheets are inserted between the two "tongues" of the clip, the tongues will be forced apart and cause torsion in the bend of the wire to grip the sheets together. too many sheets will cause the elastic limit of the material to be exceeded, resulting in permanent deformation. ==shape and composition== thumb|left|120px|paper clip paper clips usually have an oblong shape with straight sides, but may also be triangular or circular, or have more elaborate shapes. the most common material is steel or some other metal, but moulded plastic is also used. some other kinds of paper clip use a two-piece clamping system. recent innovations include multi-colored plastic-coated paper clips and spring-fastened binder clips. ==history== according to the early office museum, the first patent for a bent wire paper clip was awarded in the united states to samuel b. fay, in 1867. this clip was originally intended primarily for attaching tickets to fabric, although the patent recognized that it could be used to attach papers together. fay received u.s. patent 64,088 on april 23, 1867. although functional and practical, fay's design along with the 50 other designs patented prior to 1899 are not considered reminiscent of the modern paperclip design known today. another notable paper clip design was also patented in the united states by erlman j. wright in 1877. this clip was advertised at that time for use in fastening newspapers. thumb|right|200px|middlebrook 1899 patent for a paper clip machine showing that the gem was already in common use (top and bottom) the most common type of wire paper clip still in use, the gem paper clip, was never patented, but it was most likely in production in britain in the early 1870s by "the gem manufacturing company", according to the american expert on technological innovations, professor henry j. petroski.petroski, henry: "polishing the gem: a first-year design project", journal of engineering education
American_inventions Fasteners Office_equipment Stationery