Procedural Props for Garry's Mod!
This addon allows you to modify and customize a variety of shapes in real time with an ingame editor, with support for duplicator, constraints, and fully working physics. In fact, most tools that work on ordinary props should also work on primitive props.
To use, just spawn one from the spawnlist on the left side of the screen, and then open the editor with the context menu.
https://steamcommunity.com/sharedfiles/filedetails/?id=2840295308