Short answer: Concertina wire is coiled wire with sharp razor barbs, used on top of walls and fences at factories, borders and defence sites. Standard types are BTO-22, CBT-60 and CBT-65.
Concertina razor wire (also called razor coil, BTO wire, barbed coil, or security coil) is a coiled wire with sharp razor blade-shaped barbs stamped into it at regular intervals. Unlike traditional barbed wire, the razor barbs cause serious injury if touched, making it a high-security deterrent. It is used on top of perimeter walls and fences at factories, warehouses, prisons, border fencing, defence establishments, and high-security industrial sites. Standard types are BTO-22 (single coil, 450mm diameter) and CBT-60 and CBT-65 (concertina double coil, 600mm and 650mm diameter). The India-Bangladesh border fencing in West Bengal uses large quantities of concertina wire. It is also used extensively by the defence sector and industrial security installations across the Northeast.
