When the war breaks out, the armies had only anti-tank rifles and grenades to destroy a tank by infantry. Then, the tanks are low armored so the anti-tank bullets can penetrate the armor. As more and more powerful tanks rolled onto the battlefield, the need arose for more powerful anti-tank weapons. Whereas the Americans developed their rocket-launcher the Bazooka and the Germans their recoilless gun the Panzerfaust, the British went in yet another direction. Their PIAT (Projector, Infantry, Anti Tank) launched a HEAT projectile using a spring. This method, unlike the Panzerfaust and Bazooka created no smoke at all, however it had some unique problems of its own. When fired the spring would push forward a heavy 5kg ballast, which would then also ignite a small charge on the projectile, pushing the ballast back and locking it into place again, so the spring would not have to be cocked after firing. This system was quite unreliable and often failed to lock the spring back in place. The operator would then have to cock the PIAT manually, which required a force of 900 Newton. The ballast also made the PIAT very heavy. It was first used in the Sicily campaign and remained the primary portable anti-tank weapon for the British throughout the war.
The sight had holes for (from Up to down) 30, 60, and 120 m.