This is not a question, just a sharing of something, that may or may not be helpful.
This afternoon while working on a Project, I had to drape an imported DWG, (Topography drawn by others), onto a large imported terrain from Geolocation.
I had done the initial cleaning up of the DWG in BricsCAD to remove all the unwanted geometry.
Imported the DWG into Sketchup and then draped it on the terrain, to allow me to apply textures to the relevant areas.
When I tried to select the paving area, it turned out it was not formed by closed edges. There was a pesky gap somewhere. I started going around the whole perimeter of the paving area to no avail. I could not see the gap.
Anyway, I then had an idea to show Hidden Geometry. This meant that I could travel around the paving area edges, selecting the faces formed by the paving edges and the hidden edges. Gaps were then identified quickly as any gaps caused the whole hidden face to be selected, not just the bit on the inside of the paving area. Allowed me to be more selective int he area I was examining. Where no problems existed, only the part of the face enclosed by the paving edge and the hidden edges was selected.
It turned out that the gaps were so small, there’s no way I would have found them otherwise.
Anyway, hope that might help someone along the line.