3d modelling software

Rob asked I've found OpenSCAD to be perfect for things like brackets, machine parts and so on. It's no good for figurines and other complex curved objects, perhaps use Blender for those. It also has its quirks and limitations such as being notoriously crappy at fillets, but even passable versions of those can be achieved now (see https://www.thingiverse.com/thing:4932117). I like being able to model solids from first principles, where the model's source is literally just that, a piece of source code. Easy to email or print. And I know that my model is always going to be around and not beholden to the cloud. You can get the program at http://openscad.org/ Being code I think anyone here on cctalk could pick up the gist of it in only one or two clock cycles. Some public models of mine at https://www.thingiverse.com/1944gpw/designs feel free to look at the source which I provide with all my public designs. An STL file is not a source file, but a .scad file is, and is naturally parametric. And only three consecutive keypresses required to generate an STL file ready for slicing: F5 (preview) then F6 (render) and then F7 (save STL). That's fantastically simple. Other free CAD apps I've used include FreeCAD but I found it crashed when trying to import machine-generated DXF files of involute gears with line segments that weren't properly closed. OpenSCAD imported them no problem. Why not give it a try, I'm sure it would be ideal for your guide rails. Steve.