The opposing faces can be meshed with either quadrangles or triangles,
while the side faces should be meshed with quadrangles only.
-\image html image157.gif
+\image html image157.gif "Prism with 3D extrusion meshing".
As you can see, the <b>3D extrusion</b> algorithm permits to build and to
have in the same 3D mesh such elements as hexahedrons, prisms and
