About Connecting Mesh Elements
To create new faces, you can connect the following types of mesh elements:
One or more sets of faces and edges of multiple shapes.
Two or more faces or edges to add new faces to a region of the control mesh. The selected faces or edges get connected with parallel edges, thus creating new faces.
More than one set of faces. That is, you can select two faces on one side and two corresponding faces on the other side of a control mesh and connect them.
Three connected faces.
More than four edges or faces and connect them. A control mesh is created with quad faces. The connect operation works only if you have selected even number of faces or edges.
You cannot connect mesh elements in the following cases:
Selected faces share an edge of an unselected face.
Selected edges share the same unselected face.
Selected edges share the same unselected edge.
Selected edges share a single vertex.