When is 'outer shell' option available?

I have used the ‘outer shell’ option once or twice on SketchUp for Web, but now when I select two groups and right-hand click them, I don’t seem to get the option…
Do the groups have to be solids? Must they be ‘clean’, ie without any curved/masked geometry? Or what am I missing?

Yes, each of the selected objects must be a SketchUp solid for outer shell to be available.

Ok, thanks.

I’m struggling to make this object a solid; as far as I can see it should okay, but SketchUp doesn’t say so…
Could anyone tell me what’s wrong with it?
Don’t try and figure out what it’s supposed to be, you won’t manage. :smile:
Non-solid.skp (226.6 KB)

I assume you created it with followme. The extrusion path is still present inside the object (followme does not delete the path). If you erase the path, the object becomes solid.

Thank-you very much.