At the beginning, the trio have hitched a ride, with Compo (his double) on the top of the tall vehicle. When getting off the vehicle, seen from the side, Compo's double gets off at the opposite side from the audience POV. Seen coming toward the vehicle is Bill Owen's (Compo's) shadow. As Compo comes into the audience's view, the double's shadow is seen moving away before the vehicle drives off.
At the end, Compo's double, seen from the legs down, is walking on a jagged wall. He turns and drops down behind the wall. The real Compo, Bill Owen, then stands up a couple feet from where the double landed.