The arrangement of gears seen above is named a worm and worm wheel. The worm, which in this example is usually brown in colour, just has one tooth but it is worm gear and worm wheel similar to a screw thread. The worm wheel, coloured yellow, is like a standard equipment wheel or spur equipment. The worm at all times drives the worm wheel circular, it is never the opposite way circular as the system tends to lock and jam