Close an opening like this one (mesh)

[AndersDeleuran]

Here’s another approach that gets the naked mesh perimeters and meshes these:

180516_FillMeshHoles_00.gh (5.2 KB)

If you wants quads, you can add:

fm.Faces.ConvertTrianglesToQuads(3.14/90.0,0.875)

After line 8.