+<li><b>Total thickness</b> - gives the total thickness of element layers.</li>
+<li><b>Number of layers</b> - defines the number of element layers.</li>
+<li><b>Stretch factor</b> - defines the growth factor of element height
+ from the mesh boundary inwards.</li>
+<li><b>Extrusion method</b> (available in 3D only) - defines how
+ positions of nodes are found during prism construction and how
+ the creation of distorted and intersecting prisms is prevented.
+<ul><li><b>Surface offset + smooth</b> method extrudes nodes along the normal
+ to the underlying geometrical surface. Smoothing of the internal surface of
+ element layers is possible to avoid creation of invalid prisms.</li>
+ <li><b>Face offset</b> method extrudes nodes along the average normal of
+ surrounding mesh faces to the intersection with a neighbor mesh face
+ translated along its own normal by the thickness of layers. The thickness
+ of layers can be limited to avoid creation of invalid prisms.</li>
+ <li><b>Node offset</b> method extrudes nodes along the average normal of
+ surrounding mesh faces by the thickness of layers. The thickness of
+ layers can be limited to avoid creation of invalid prisms.</li>
+\image html viscous_layers_extrusion_method.png "Prisms created by the tree extrusion methods at the same other parameters"
+</ul></li>
+<li><b>Specified Faces/Edges are</b> - defines how the shapes specified by
+ the next parameter are used.
+<li><b> Faces/Edges with/without layers</b> -
+ defines geometrical faces or edges on which element layers
+ either should be or should not be constructed, depending on the
+ value of the previous parameter (<b>Specified Faces/Edges are</b>).
+ Faces (or edges) can be selected either in the Object Browser or in
+ the VTK Viewer.
+ \note A mesh shown in the 3D Viewer can prevent selection of faces
+ and edges, just hide the mesh to avoid this. If a face, which should be
+ selected, is hidden by other faces, consider creating a
+ group of faces to be selected in the Geometry module.<br>
+ To avoid a long wait when a
+ geometry with many faces (or edges) is displayed, the number of faces
+ (edges) shown at a time is limited by the value of "Sub-shapes
+ preview chunk size" preference (in Preferences/Mesh/General tab).
+
+
+ If faces/edges without layers are specified, the element layers are
+ not constructed on geometrical faces shared by several solids in 3D
+ case and edges shared by several faces in 2D case. In other words,
+ in this mode the element layers can be constructed on boundary faces
+ and edges only, and are not constructed on internal faces and
+ edges. There is an exception to this rule: if a hypothesis is
+ assigned to a sub-mesh, the element layers can be constructed on
+ boundary faces/edges of the shape of this sub-mesh, at same time
+ possibly being internal faces/edges within the whole model.
+ \image html viscous_layers_on_submesh.png 2D viscous layers constructed on boundary edges of a sub-mesh on a disk face.
+
+ If you use \b several hypotheses to define viscous layers on faces of
+ one solid, keep in mind the following. Each hypothesis defines a set
+ of faces with viscous layers (even if you specify faces without
+ layers). The sets of faces with viscous layers defined by several
+ hypotheses should not intersect, else the module won't add an
+ hypothesis that is incompatible with another one. <br>
+ Also you can't define different number of layers on adjacent faces
+ of a solid.<br>
+ This logic is also valid for the 2D hypothesis.
+</li>