Solid inspector enigma...?

[Ted0711]

I’m still working on a box which I want to print, but there is one last obstacle. When I want to union to make the object solid I get an error message. In solid inspector the message says something about the borders. I understand the words but not the message. What should I do to be able to print this open box?

[DaveR]

It’s telling you there are edges that need a face. A simple way to think of how something can be solid is that every edge must be shared by EXACTLY two faces. In the screen show you show, the edges highlighted in red are only shared by one face, not two.

[Box]

As an example of what Dave is saying, the box on the left cannot be a solid since the faces have no thickness. While the box on the right is a solid because all faces have a thickness. Basically if you can see the blue/grey backface colour then something is missing.

[Ted0711]

Thanks very much. I start working on it.