When I wrote Greenberg’s Guide to Märklin Z in 1988, Woodland Scenics already dominated the market for model railroad scenery products. In the intervening years, this domination has grown, with just cause. Woodland Scenics has continued with a thoughtful approach to model railroading, providing products that get you toward a completed and interesting model railroad. At the heart of the SubTerrain system is a simple sheet of plywood. To quote Woodland Scenics:
“The SubTerrain System consists of lightweight foam components, such as Risers*, Incline Sets*, Profile Board and Foam Sheets. These components allow modelers to easily create terrain with hills, mountains, valleys and low-lying areas on any layout. Modelers no longer need to use heavy plywood or make complicated calculations. SubTerrain System layouts are built without power tools and never make a dusty mess.”
That’s the truth. In particular, their approach to model railroad construction can be done either slowly with an inexpensive tool or more quickly with a moderately priced tool. The elements of the system can be glued in place with a hot glue gun or glued in place with bottled glue. The Profile Boards can be cut with a hot wire or with a long bladed knife. Perhaps equally important is that their broad range of products are commonly available at hobby shops and are rarely on backorder with those shops.
Rather than rewriting what Woodland Scenics has already written well, please refer to their web site. In particular, look at the information about the SubTerrain System and the Mod-U-Rail System. You may very well find what you need for layout construction.