I suggest you read the API... https://developers.google.com/sketchup/docs/ The entities.add_...() methods do want you want... You'll also need to understand Transformations [simple will do!] used to locate some things like 'instances'... and how to create objects like Point3d and maybe Vector3d... There many freely available snippets and full-scripts, that already do what you seek, so there's no need to reinvent the wheel from scratch - just understand what you are doing... I might move this into the Developers' Forum... [EDIT: done.]