On the SGV source-code directory, there are two examples of geometry descriptions with the names sgv_geo1_ex.inp and sgv_geo2_ex.inp. They are also given at the end of this manual, as appendix B It is a good idea to use one of these files as a template when You write Your description. These descriptions corresponds to the DELPHI detector at LEP, and the proposed detector for TESLA, respectively . In the following, we give a few examples of the technique of writing the descriptions.