Hi Michael,
dont know how can i fix this. It looks sooo simple but cant create a solid from this construction.
Can you help please?

1. i have 2 curve for a sweep operation.
2. After sweep the naked edges are only at the opened side. That ok.
3. If i select the naked edges and make a planar then join all of them i get only a joined surface.

How can i get it solid ?

Thanks