There is no substitute for a properly designed steel bumping post at a track end. Expensive concrete posts shift and crack. Wooden ramps quickly become deformed under impact. Retaining walls are usually too light to function as a car stop. However, if conditions do not permit the use of a steel bumping post, the Shock-Free Head can be mounted on a flat vertical surface. Consult local civil engineer regarding capacity of the vertical surface you intend to use. The W-C-H Attaching Fixture, a 145 pound steel weldment.