Hobby terminology in plain English

Scenic base
A layout's scenic base is the foundation for all of its scenery, including roads, grass, trees, and rocks. An inexpensive scenery base can be made using a lightweight support structure, such as cardboard strips glued together, covered with layers of plaster-soaked gauze or paper towels. Another type of base you can use is made from screen wire formed to make hills and valleys and covered with plaster.

A more recent approach to making scenery bases uses one or more layers of foam insulation board glued together and carved to a desired shape.

Ground foam
Ground foam is a material used to represent grass, leaves, soil, weeds, and other foliage. Manufacturers make it by grinding up foam rubber and dying it various colors to represent grass and soil. Ground foam is typically one of the first layers of scenery to be installed after the scenery base is complete. The scene in fig. 6 uses a variety of sizes.

Rock molds
You can make your own highly detailed rock formations by using rubber rock molds and Hydrocal plaster or plaster of paris. Rock molds are offered by many manufacturers, come in a variety of sizes, and are easy to use. Simply fill the mold with plaster and then remove the rock casting when the plaster has set. After the plaster has dried, glue the casting to the layout and paint it.

Fig. 6. Ground foam. This trackside hill on the Milwaukee, Racine & Troy has several layers of ground foam on it. Not how the different colors and sizes of foam give detail and texture to the surface, adding realism.