Good way to add a backside to a grid (3D printing) I want to add a backing to a grid like structure. I'm wondering if what I did is a good way to do that. I first selected the faces that make up the grid and extruded them out 4mm. Then I closed off the inner rings of each grid square with faces (f). Finally I ended by closing off the outer rings of each grid square. What I'm wondering now is that inside of this backing there are sections that connect from one grid to another and so the back is not completely hollow.

The goal is to 3D print this model.

Maybe this picture will be more clear:
To fill the back face, first make sure you don't have any inner face, so select the face loop with alt right click and delete. Then with the same alt right click select the edges loops and fill the faces with F. Is it what you want?