A waggonway might need unavoidably to slope in the absence of any cutting or to reach staithes. This section is called an incline. Wagons would be need to run up or down it. Gravity could be employed on the downhill slopes. To assist horses used stationary winding engines were employed to haul the wagons up slopes - lowering the other wagons safely. Alternatively use of ropes or cables allowed those wagons going down a slope to pull other wagons up by gravity alone, called self-acting inclines. These mechanisms were introduced from the 1750s AD.