# FLAC3D Commands and FISH

The FLAC3D model consists principally of zones and structural elements. Zones are composed of faces and gridpoints. Construction of zones for a FLAC3D model may occur via direct commands, such as zone create. In addition, FLAC3D provides facilities in the user interface for construction of zones by extrusion, and by 3d block construction (building blocks). Actions within these facilities are translated into extrude commands and building block commands, respectively. All of the aforementioned are considered FLAC3D model objects throughout the documentation. The commands and FISH functions used to work with them are described in this section.

In addition, a FLAC3D model may include structural support elements. These too are model objects, but these objects are shared also with other Itasca software (3DEC), so all descriptions, command, and FISH documentation for them are found in Structural Elements in the Program Guide section.