This is to barbed wire what the Pentium is to the 486. Little, razor-sharp blades fastened to wire. Usually, there is a group of three blades set at angles of 120 degrees to each other every ten centimetres or so. The blades aren't simple blades, either, their ends are curved inwards so there are six sharp points in every group of blades, and the entire affair can not only cut you up badly, but you can also get stuck in it. The fiercest kind of razor wire is NATO wire.