# Need help figuring out how to fix this non-manifold 3d print

I am making a checker board type piece as pictured. I used the loop cut and slide to break up the rectangle into smaller rectangles and then extruded them upwards. It is now showing as a non-manifold problem and I can't figure out how to fix it. Thanks

There are non-manifold regions in your mesh. You should extrude faces upward in another way and it will work.

Why non-manifold

The reason for non-manifold in this case are areas with no thickness. For example, this connection:

The edge, which consists from selected vertice and bottom one, shares 4 faces and perfectly fits reason for being non-manifold.

You can notice that non-manifold is selected only in areas where these connections are present:

Note area in top middle - there isn't any face extruded further, hence there isn't any zero-thickness edge.

How to repair

Delete those faces and fill holes in mesh in order to make this surface flat and solid again, select the pattern how you'd like to extrude and use Extrude Individual operator with Alt+E.

After individual extrusion faces aren't connected to each other and do not have any shared edges.

• @LarryGuthrie small note - there's another way to avoid extrusion to become non-manifold again after removing doubles. On the first step of the repairing process with faces-to-be-extruded selected inset them (press I) just a bit. Then extrude as desired; no scaling needed after that because extrusion already won't have any shared vertices. Feb 20, 2016 at 23:28