— non -removable — is part of the concrete itself (foundation)
Consider the process of building formwork itself.
For the base, it is necessary to nail on driven wooden bars with nails, from the inner surface of the formwork, plywood (or boards). So that such a design is as strong as possible, you can fix with a distance of one meter in addition to the outside with a distance. After all these events, we proceed to fill the foundation (concrete).
