Hi Nathi,
“…edges touch at least 2 faces…”
That should be all Edges are connected to exactly 2 Faces. But then that is also the only ‘rule’ that decides if a Mesh is Manifold. (There are of course other definitions of Manifold, but this is probably the simplest…)
But Manifold alone is not enough to be Printable (sharp angles, for instance are no good). The Addon checks for other problems as well, if I’m not mistaken.
