Barbed wire is a fencing material consisting of a metal cable with regularly spaced sharp projections. The cable usually consists of two wires twisted around each other to add strength and to allow the cable to expand and contract with temperature changes without breaking. The sharp points, called barbs, usually consist of short pieces of wire twisted around one or both of the cable wires.
Barbed wire is usually made of steel, which is an alloy of iron and a small amount of carbon. The raw materials required to manufacture steel are iron ore, coke (a carbon-rich substance produced by heating coal to a high temperature in the absence of air), and limestone. To prevent rusting, the steel wire is usually coated with zinc. Sometimes the steel is coated with aluminum, and occasionally the barbed wire itself is made of aluminum.
Barbed wire was adapted for military use during the Boer War and used in enormous quantities during World War I. Although barbed wire is often used for security, agriculture still accounts for 90% of its use. Many people collect antique barbed wire, with some rare specimens selling for hundreds of dollars. Hundreds of collectors attend the annual Barbed Wire Festival in La Crosse, Kansas, home of the Barbed Wire Museum.