+<b>Free faces</b> selects 2D mesh elements wich belong to less than two volumes.
+</li><li>
+<b>Faces with bare border</b> selects 2D mesh elements having a free border without an edge on it.
+See also \ref bare_border_faces_page "Bare border faces quality control".
+</li><li>
+<b>Over-constrained faces</b> selects 2D mesh elements having only one border shared
+with other 2D elements.
+See also \ref over_constrained_faces_page "Over-constrained faces quality control".