There are three wooden balls on the bottom of the galvanometer base that form a tripod, supporting the instrument. These screw into and out of the base. Thus, rotating one of these spheres causes it to come further or closer to the base, effectively changing the height of this support. By adjusting these three supports through rotating them, you can adjust the base to be horizontal. This leveling mechanism is very important, for the coil must be perfectly horizontal in order to allow the needle within it free range of motion.