... important consideration for models is to keep it below the wheel flanges. I'm still undecided about how to blend the side of the jaw into the chair base and rail seat. I have removed the silly angled socket in the rail seat which I had previously. On the prototype it is a spherical fillet radius, but that would involve a silly amount of code. On the outer jaw I used a few simple facets instead, although I'm not convinced it looks right. It is easier to see without the rail in place: 2_241247_000000000.png This view also shows the tapered ends of the key, to ease rail threading and reduce stress on the chair. Time for a boiled egg. Martin. posted: 24 Nov 2018 19:17 from: Andrew Barrowman Hi Martin, I'm assuming we'll be able to randomize the rotation of the screw heads. Seriously, looks good. Before you go too much further, if you can generate a complete model we can easily find out file size etc. Obviously a lot of the detail you are adding won't be visible ...