Slat armor (or slat armour in British English), also known as bar armor, cage armor, and standoff armor, is a type of vehicle armor designed to protect against high-explosive anti-tank (HEAT) attacks, as used by anti-tank guided missiles (ATGMs) and rocket-propelled grenades (RPGs). Operation Slat armor takes the form of a rigid slatted metal grid fitted around key sections of the vehicle, which disrupts the shaped charge of the warhead by either crushing it, preventing optimal detonation from occurring, or by damaging the fuzing mechanism, preventing detonation outright. Although slat armor is effective against incoming missiles, it does not offer complete protection – as many as 50% of missile impacts are unimpeded by the slat design. Slat armor is more likely to be effective if the cage spacing is less than the diameter of the incoming RPG round, which is commonly 85 mm. Combat history World War II The German Wehrmacht was the first employer of cage armor during World War II, using Drahtgeflecht-Schürzen (English: "wire mesh skirts") to fortify its tanks against shell fire. It was found to be just as effective as the steel plate Schürzen also being utilized. In March 1943, Adolf Hitler ordered all new Sturmgeschütz, Panzer III, IV, and Panthers be outfitted with Schürzen of either the wire mesh or steel plate type. However, the wire mesh was not as easy to mass-produce as steel plate Schürzen or armored skirts. Soviet Red Army tanks, faced with the new and highly effective German Panzerfaust, were similarly outfitted with "bedspring" armor made from expanded metal mesh grating panels. However, Schürzen were designed to stop Soviet PTRD-41 anti-tank rifles, and proved ineffective against Bazooka and Panzerschreck anti-tank rockets in US and German tests. Cold War era In the Vietnam War, slat armor was commonly used on the sides of American patrol barges and boats. The CCB-18 is a surviving example of the Mobile Riverine Force which used such armor. Wire fencing was also placed on vehicles such as the M113 to defeat Vietcong RPGs. The Swedish Stridsvagn 103 of the same era employed a much heavier front-mounted metal grid to protect against incoming projectiles. Modern era In modern times, slat armor has seen use on the Israel Defense Forces (IDF) Caterpillar D9R armored bulldozer, the Force Protection Buffalo MPV MRAP vehicle, the General Dynamics Stryker, Ukrainian BTR-4, the Warrior infantry fighting vehicle, the M113 APC, the British Challenger