Simple machines include the pulley, inclined plane, lever, wedge, screw, and wheel and axle. A pulley uses a grooved wheel and rope to move loads, an inclined plane connects different levels with a slanting surface, and a lever lifts loads using a stiff bar resting on a fulcrum. A wedge cuts materials apart with a sharp edge, a screw holds things together or lifts materials using an inclined plane wrapped around a pole, and a wheel and axle lifts loads using a wheel with a central axle.