Woodland Scenics #C1250 Tunnel Liner Form This innovative mold is ideal for casting realistic rock walls and ceilings for scale tunnels on your pike. It is designed to form half of either a single or double liner section with each pour of Lightweight Hydrocal. Use a spatula to fill the Tunnel Liner Form with Lightweight Hydrocal, join two half sections on top with a strip of Plaster Cloth to form a hinge, and join completed units on one side for a longer tunnel. The unattached side can be raised for track maintenance.