This device illustrates the workings of a system of gears. When you turn one gear, the meshed teeth cause the other gears to rotate as well. The second gear turns in the opposite direction as the first, and the third gear turns in the same direction as the first. By meshing together a series of gears, you can transmit force from one place to another, as well as change in the direction of applied motion. This classic wooden model offers children a basic concept of the laws of physics. Desktop sized.