An extreme instance of the pedrail's capacity would be afforded by the ascent of a flight of steps . In such a case the three "peds" carrying the weight of an axle would not be on the same level. That makes no difference, because the frame merely tilts on its top and bottom pivots, the front of the rail rising to a higher level than the back end, and the back spokes being projected by the rail much further than those in front, so that the engine is simply levered over its rollers up an inclined plane. Similarly, in descending, the front spokes are thrust out the furthest, and the reverse action takes place.