Snakes have scales on their belly skin which help them move about. On a flat surface, the body weight is continuously redistributed for maximum friction, and the scales provide grip. Researchers at the Georgia Institute of Technology have made detailed studies of the movement of the milk snake. The result, which they call terrestrial lateral undulation, reveals complex motion. On a smooth surface, the snake pushes slightly upward and forward while gripping with its scales. Detailed measurements showed 65 percent of the forward motion comes from contact friction and the other 35 percent from the forward travel while lifting parts of the body just above the surface.