I can't close a surface

Somehow I ended up with that little open section on my model. I have drawn around the corners several times with the pencil tool trying to close the surface but to no avail. I may have a bunch of lines there that shouldn’t be there but I can’t see any. Can someone tell what I’m missing?

BottomV2a.skp (34.7 KB)

draw a diagonal, if all you need is to fill the void…


I looked at the file you posted. The problem is that the void you are trying to close is not a plane, that is, the 4 corners of the rectangle don’t line up on one plane so if a surface were drawn including those 4 points it would be a curved surface, which SKUP don’t play. If you look from the side you can see that the bottom is skewed.
I suspect something went wrong in the push/pull phase of your build that led to the bottom face being different geometry than the top. It also appears that the long skinny section of your keyhole is not centered on the larger circle. This may be intentional but it has made a made the intersection tricky.
As John said you can solve this by drawing a diagonal line across the empty box creating two triangles (any three points are a plane), but you will end up with some odd shapes in that corner. If this quick fix works for you then great.

If you need nice flat walls around your keyhole then I was able to fix the drawing quickly by erasing the walls and bottom of the keyhole (side away from the outside walls) then I push/pulled the top surface down again with the option button down to add a new surface. This resulted in closed geometry. Good Luck!

BottomV2b.skp (42.9 KB)

There are geometrical errors, did not check total model but probably same type of errors. If yoy fix one local area and not total you will have problems later

Thank you for your replies. You’ve given me several new tools and techniques to work with although I’m not sure quite how I got the model to that peculiar state to begin with.