Woodland Scenics C1236 Classic Rock - 5x7 Mould Use this mold to make rocks for riverbanks, road embankments or anywhere you want an outcropping of large rocks. .About Terrain Formation Model any type of terrain in any geographic area with spectacular results. Each Terrain System product includes easy-to-follow, illustrated instructions. *Hydrocal® is a U.S. Gypsum registered trademark.