Drawings of a switchback with a retaining wall. In the drawings the text reads, Backslope, Inslopped trail tread with 5% slope, fillslope, 5 ft min., Outsloped trail tread, Retaining wall, Original ground plane, Drainage swale, Upper (descending) leg shoulder with 10% max. slope, Begin inslope 20 ft from landing, 5 ft min. radius landing, Crowned landing slope 5% in all directions, Lower (climbing) leg shoulder with 15% max. slope, Outslope with 5% max. slope, and Downslope.