Blender 3D Printing by Example

Missing faces or holes

Perhaps I decide I want to make the house figurine hollow to save on material cost. A misguided approach would be to delete the bottom faces of the house. The house looks hollow in Blender, but all the edges around the bottom are only connected to a single face and are therefore non-manifold. You can also think of it as the walls of the house no longer have a thickness. A better way to achieve my goal would be to insert and extrude in, which makes sure all edges have two connected faces and my walls have a thickness:

Deleting the faces at the bottom of the House Figurine would leave all the walls without a thickness ...