 right|250px|thumb|concertinered razor wire concertina wire or dannert wire is a type of barbed wire or razor wire that is formed in large coils which can be expanded like a concertina. in conjunction with plain barbed wire and steel pickets, it is used to form military wire obstacles.barbed wire entanglements. during world war i soldiers manufactured concertina wire themselves, using ordinary barbed wire. today, it is factory made. == origins == right|thumb|a sketch of a typical concertina wire obstacle thumb|concertina wire can be a feature of prisons. in world war i, barbed wire obstacles were made by stretching lengths of barbed wire between stakes of wood or iron. at its simplest, such a barrier would resemble a fence as might be used for agricultural purposes. the double apron fence comprised a line of pickets with wires running diagonally down to points on the ground either side of the fence. horizontal wires were attached to these diagonals. more elaborate and formidable obstructions could be formed with multiple lines of stakes connected with wire running from side-to-side, back-to-front, and diagonally in every possible direction. effective as these obstacles were, their construction took considerable time. barbed wire obstacles were vulnerable to being pushed about by artillery shells; in world war i, this frequently resulted in a mass of randomly entangled wires that could be even more daunting than a carefully constructed obstacle. learning this lesson, world war i soldiers would deploy barbed wire in so-called concertinas that were relatively loose. barbed wire concertinas could be pre-prepared in the trenches and then deployed in no-man's-land relatively quickly under cover of darkness.  concertina wire packs flat for ease of transport and can then be deployed as an obstacle much more
Area_denial_weapons Fortification_(obstacles)