--- /dev/null
+.. _group_of_underlying_elements_page:
+
+************************************
+Group Based on Nodes of Other Groups
+************************************
+
+
+To create a standalone group of entities basing on nodes of existing reference groups, in the **Mesh** menu select **Group of underlying entities**.
+
+The following dialog box will appear:
+
+.. image:: ../images/dimgroup_dlg.png
+ :align: center
+
+In this dialog box specify
+
+ * the resulting **Group name**,
+ * the **Elements Type** of entities of the resulting group,
+ * the criterion of inclusion of a mesh entity to the result group, which is **Number of common nodes** of the entity and the reference groups:
+ * **All** - include if all nodes are common;
+ * **Main** - include if all corner nodes are common (meaningful for a quadratic mesh)
+ * **At least one** - include if one or more nodes are common
+ * **Majority** - include if half or more nodes are common
+
+ * select reference groups,
+ * If **Include underlying entities only** option is activated an entity can be included if it is based on nodes of one element of a reference group.
+
+
+In the figure below, there are two reference Volume groups:
+
+.. image:: ../images/dimgroup_src.png
+ :align: center
+
+.. centered::
+ Reference groups
+
+In this case the following results for Faces, Edges and Nodes are obtained:
+
+.. image:: ../images/dimgroup_2d.png
+ :align: center
+
+.. centered::
+ Faces
+
+.. image:: ../images/dimgroup_1d.png
+ :align: center
+
+.. centered::
+ Edges
+
+.. image:: ../images/dimgroup_0d.png
+ :align: center
+
+.. centered::
+ Nodes
+
+**See Also** a sample TUI Script of a :ref:`tui_create_dim_group` operation.
+
+
