During the Vietnam War, US Forces began building portable fencing structures on their vehicles .This was chain link fenc or very tight barbed wire. The goal was two fold. First, the fence could catch the round in mid-flight, holding it and keeping it away from the vehicle. If the round detonates away from heavy armor, then it probably will not penetrate the armor. Most RPG-7 rounds are designed as shaped charges, so they need to be a set distance from the surface of the target when they go off, or they are not effective in penetration. Rounds that have a self-destruct fuze will explode 5 second after firing, even if trapped in defensive fencing. This is a danger to soldiers who are un protected. While the AT rounds are not designed as anti-personnel, there can be enough fragmentation and blast to kill or cause other casualties to those near the explosion. The second reason for the fencing is due to the manner in which the traditional RPG-7 rounds operate. There is a double cone in the front of the stand-off area. These two cones are intended as the path for the peizo electric fuze to ignite the main fuze on the shaped charge. It is quite effective, but if the round strikes the fencing and this cone area is distended and the cones touch, the fuze can't operate- it is short circuited. Newer rounds have a bypass system in place, so the best the defender can hope for is to hold the round in fencing, away from the skin of the vehicle, when it explodes. Damage to unprotected personnel can be expected. In the event that the nose fuze strikes a strand of the fence, the round will detonate away from the vehicle, nullifying the shaped charge effect. The shaped charge can, however, penetrate light armor from sevreral feet away.