Rear Differential Lock is a device that can temporarily cancel the differential function of the rear axle so that the two rear wheels rotate at the same speed. Under normal conditions, a differential allows the vehicle's left and right wheels to rotate at different speeds to accommodate differences in path when cornering. However, when one wheel of the vehicle is on a low-traction surface (such as mud, snow, or ice), an open differential causes most of the power to be transferred to the slippery wheel rather than the grippy wheel.