When the Lidgerwoods were in the clear along came another locomotive pushing the spreader which was another plow device operating at the level of the rails.  The plow blades were positioned at the proper angle by air cylinders.  There was an air tank on the rear of the unit which was next to the locomotive.  the air tank was charged by the locomotive's air brake compressor.  When moving from one area to another, the blades could be retracted to within the car body thus being able to pass obstruction such as switch stands.