Sidewinding is the type of locomotion that lets snakes move across loose desert sand without sinking.
In sidewinding, a snake lifts sections of its body and places them down in a sequence of angled contact points. The body forms a series of nearly parallel tracks, reducing the amount of weight pressing into any one patch of sand. This helps the snake cross surfaces where ordinary lateral undulation would cause its body to slip or bury itself.
Sidewinding is especially associated with desert vipers, including the sidewinder rattlesnake of North America and several horned vipers of Africa and Asia. The technique also helps snakes keep much of their body away from extremely hot ground.
Sidewinding is not the same as lateral undulation, the familiar winding movement used on firmer ground. It is also different from concertina locomotion, in which a snake anchors parts of its body while extending and pulling forward other sections.