LeoCAD is a graphical interface, based on the LDraw graphical engine. With LeoCAD it’s possible, to stack multiple parts on top of each other, like playing with Lego.
Like LeoCAD, the LDraw system is designed to virtual play with Lego. It has a massive library of Lego parts, which is also supported by main people. There are also 2 other main stream CAD editors, but I have choose to use LeoCAD also, since it could be installed on 3 different operating systems.
The LDraw system is also very well documented and basically I’m re-using this system for vintage building toys, by simply replacing the parts library with different parts, see picture:

In the LeoCAD menu -on top of this page- you find some basic information, how to install & use LeoCAD.
More information on tips & tricks will follow..