From OpenSCADAWiki
Main frames
Contains elements-frames of the template and end types, as well as elements-widgets and panels from which they are built and used. These frames are intended to be placed in the project tree of the pages, built on the concept of the signal objects of the root page "RootPgSo". However, they may be located as separate entities or as part of your own concept of the page management, but it should be take in account that frames often refer and call certain control panels of the common usage and related elements!