Best way to close this open wall section in Edit Mode?

Blender 4.4.3

I want to close the open area and create a proper face (see the GIF attached). However, on one side there are no vertices or edges that I can select, so I can’t simply select the boundary and press F.

What would be the correct way to create the missing geometry and close this area?

I’ve attached a gif showing the current situation. Thanks!

2026-08-18_09-21-35

Hi,
99,9% it seems you have duplicate geometry here.

  1. edit mode > select all
  2. M (merge) > by distance
  3. then retry adding the face selecting the 3 edges

Also, I don’t know your needs and your workflow but you are doing this in a complicated way. In most cases, to build standard walls, you just need to use the solidify modifier on lines.
Solidify:

select the 2 vertical edges and then press F.

It will create the quad face to close that vertical wall.

The under part of the wall will still be opened…for that you could close doing the same…select a couple of edges and press F… or select the non-manifold edges with the dedicated select command and press F

uhmm..probably you’re right…I’ve tried with a simple modified box to have the same opened parts and selecting the same 3 edges I can create a quad…

You also seem to have messy topology here.

Non-manifold

This is non manifold geometry. When one edge has more than 2 faces:

It’s going to be a problem for various algorithms so you should avoid that.

It does seem like duplicate vertices would explain the issue fully, so suggested solution should work. I think you have double vert and so the geometry is like this:

So you have an edge like the one I point at with the arrow, but yours is too small to see and that’s why this happens when you hit F:

You should still address the non-manifold geometry issue and delete the internal faces. Those are just problems waiting to happen later on. Unless you have a really good reason for having that type of geometry which to be honest I really fail to imagine in this situation.