Michael that is a bit of WOOF/WOW learning to working proceedures.(For me!)
Not complaining, but was there something I missed earlier, or is this an area of missing general working method in other apps that I have not also previously grasped maybe?

It's common in drafting / AutoCAD type programs.

- Michael

Thanks Michael.
I went through a working exercise and can see the method/principle'
More stuff to allocate to my poor old brain!

I have never worked with any auto cad type programme before (Does Amapi 7.52 count?)
I guess it is a problem for those of us who started from another direction of the 3D learning curve?

So many computer 3D "languages"!