Unable to create solid

Hello, I am desperate with one object (respectively two) that should be transformed into solid, however Boolean union or Create solid commands do not work. I created the surfaces using Sweep2 command and then I tried to join them, but it always fails. I already tried to increase the tolerance, check for the intersections, add more cross-sections, join the edges, but it still does not work. I really don’t know how to stitch all surfaces together so that no gaps would occur between them. In the attachment are all surfaces and curves I used for Sweep2 commands.

Shoe_surfaces.3dm (1.2 MB)

Use the Join command to create a closed polysurface. A solid in Rhino is a closed polysurface with no naked edges.

Select the surfaces to be joined.
Join command

ShowEdges with Naked edges selected can be used to check for naked edges.

The surfaces on the left (perimeter of the sole) join into a single closed polysurface without any naked edges.

The surfaces on the right (heel) join into a single closed polysurface but with naked edges. Corresponding edges did not join because the gap between them is larger than the absolute tolerance. The gap between edges can be checked using CrvDeviation and picking the two edges as the cuves to be checked. The surfaces will need to be revised to close the gaps.

Sometimes the quickest approach to eliminating naked edges is to re-create one or both surfaces which are not joining.

Join should usually be the first choice to create a closed solid from surfaces / polysurfaces which do not need to be trimmed.

CreateSolid is for more complex situations with overlapping surfaces.

BooleanUnion works on multiple closed polysurfaces, and some situations with surfaces.