-<li>\b Mesh - containing a 1D sub-mesh on the edge, along which proceeds the extrusion</li>
-<li><b>Shape (edge)</b> - as the mesh can be complex, the edge is used to define the sub-mesh for the path</li>
-<li><b>Start node</b> - the first or the last node on the edge. It is used to define the direction of extrusion </li>
-</ul>
-</li>
-<li> <b>Generate Groups</b> checkbox allows copying the groups of
-elements of the source mesh to the newly created one. </li>
+ <li>Use \a Selection button to specify what you are going to
+ select at a given moment, \b Nodes, \b Edges or \b Faces.
+\image html image120.png
+<center><em>"Selection" button</em></center>
+ </li>
+ <li>Specify \b Nodes, \b Edges and \b Faces, which will be extruded, by one
+ of following means:
+ <ul>
+ <li><b>Select the whole mesh, sub-mesh or group</b> activating this
+ check-box.</li>
+ <li>Choose mesh elements with the mouse in the 3D Viewer. It is
+ possible to select a whole area with a mouse frame.</li>
+ <li>Input the element IDs directly in <b>Node IDs</b>, <b>Edge
+ IDs</b> and <b>Face IDs</b> fields. The selected elements will
+ be highlighted in the viewer, if the mesh is shown there.</li>
+ <li>Apply Filters. <b>Set filter</b> button allows to apply a
+ filter to the selection of elements. See more about filters in
+ the \ref filtering_elements "Selection filters" page.</li>
+ </ul>
+ </li>
+ <li>Define the \b Path along which the elements will be extruded.<br>
+ Path definition consists of several elements:
+ <ul>
+ <li><b>Mesh or sub-mesh</b> - 1D mesh or sub-mesh, along which
+ proceeds the extrusion.</li>
+ <li><b>Start node</b> - the start node of the Path. It is used
+ to define the direction of extrusion. </li>
+ </ul>
+ </li>
+ <li>If you activate <b>Generate Groups</b> check-box, the <em>result elements</em>
+ created from <em>selected elements</em> contained in groups will be
+ included into new groups named by pattern "<old group
+ name>_extruded" and "<old group name>_top". For example if a
+ selected quadrangle is included in \a g_Faces group (see figures
+ below) then result hexahedra will be included in \a
+ g_Faces_extruded group and a quadrangle created at the "top" of
+ extruded mesh will be included in \a g_Faces_top group. <br>
+\image html extrusion_groups.png
+\image html extrusion_groups_res.png
+ <p> This check-box is active only if there are some groups in the mesh.
+ </li>