Hi Tony,

> If I wanted to create a solid surface like this should do
> copying more than 4 cm above and then do a sweep around
> the surface and join?

Yes, that would work, for that part you would probably want to use the Edit > Join command to join up the individual curve segments into one big long curve so you could build that part all in one go.

But also instead of using Sweep you could use Extrude of your bottom curve to make the side piece, or also Loft which may actually be the most convenient.

For example if you have 2 curves like this:



If you want to make a surface between them, you can select them and then run the Loft command, it will then build a surface like this:



So similarly if you have 2 curves like this (each of these is a curve that has been joined together to select as a single object, not as individual separate lines anymore):



You can select them and run Loft to build this:



- Michael