Fencelike structures on patrol vehicles in Afganistan

For example on this Mastiff

At first I thought it was some kind on armour but I can’t see them stopping anything.

What are they and how do they work?

http://en.m.wikipedia.org/wiki/Slat_armor

Thank you.

The most common antitank weapon is the Soviet-style RPG. The warhead is a piezoelectric fuse in front of a shaped charge. If the warhead gets stuck between the slats and the fuse doesn’t crush, there will be no kaboom. The shaped charge itself is a copper cone (or something) that implodes to form a stream of liquid metal. This liquid metal is what actually penetrates the vehicle. If the warhead goes kaboom prematurely (from striking a slat) it will result in less-than-optimal penetration.

As I understand it, a well-designed shaped charge can cut thought steel even if it detonates several inches (or feet) away from the steel.

The solution isn’t a perfect one, but the average muj isn’t going to have an ideal set-up when he launches that RPG. Anything that can disrupt the stream from the hit is good. If you can get it to detonate away from the skin, all the better. Slat armor is a compromise between protection and weight. Otherwise an RPG will turn a Hummer into scrap metal. With the armor the troops have a bit of a chance.

Is that accurate? Reading from this article would seem to indicate that a “slug” or “carrot” solid projectile is what eventually penetrates the armor and causes the spalling, killing the inhabitants inside.

The cheap RPGs used in Iraq/Afganistant apparently are not “ideal” shaped charges. Probably, if they are not against a solid surface when the charges detonate, then most of the energy is dissipated to the sides. An RPG warhead does not have a heavy metal casing like used here : http://en.wikipedia.org/wiki/Explosively_formed_penetrator .

I think the RPG has to slam into the armor plate and the surface of the armor itself acts to help contain the blast.

But yeah, they make various anti-tank missile systems such as the Javelin that would presumably make scrap metal of any U.S. vehicle in use.