How would you make this?

[PWD]

Hi Micheus,

thanks for your reply.
Understood about dropbox! Thanks
Ok for the unit, I red it about the no-unit system of wings 3d... but it's just for reference; I think that 18WU and 5WU could be the same as 18mm and 5mm when imported in another software or exported in stl... right?
I'm wondering why it's not so trivial

Thanks a lot!
Marco