How can I turn this open surface into a solid?

Rhino Rhino for Windows
1

note: the curves are not planar, i don’t know how to make them so…
vtora chast.3dm (705.3 KB)

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image1333×750 369 KB

2

Solid.3dm (794.5 KB)

For the circular curves you can either use sweep 2 with given cross section or you can do it with revolve.

3

thanks for the answer, but i can’t open the file, beacuse im working with rhino 5.

4

Solid_r5.3dm (795.0 KB)

5

The approach is the same either way, but to be clear what do you want A or B?

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image1689×542 366 KB

They don’t currently intersect… extend almost solves that, but there is an issue in the bottom. Still not hard to correct.