You can use Surface commands to add or remove surface material in your model.
Creating Projection Curves Creating Intersection Curves Creating Through Points Curves Creating a Surface Extrude or Extrude Cut Creating a Surface Revolve or Revolve Cut Creating a Surface Sweep Creating a Surface Loft Creating a Surface Fill Knitting to Combine Faces and Bodies Trimming a Surface Creating an Offset Face or Body Extending a Surface Creating Ruled Surface