It wasn't until the 1960’s that weapons engineers developed a reliable bullet-resistant armor that was comfortable. Unlike traditional armor, this soft body armor is not made out of pieces of metal; it’s formed from advanced woven fibers that can be sewn into vests and other clothing. Hard body armor, made out of ceramic or metal plates, functions the same way as medieval iron suits worn by knights: It’s hard enough that bullets are deflected. Thus, the armor material pushes out on the bullet with the same force with which the bullet pushes in, so the armor is not penetrated.