The arrangement of gears seen above is named a worm and worm wheel. The worm, which in this example is brown in colour, just has one tooth worm gear and worm wheel nonetheless it is 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 contrary way round as the system will lock and jam
