--- /dev/null
+.. _merging_elements_page:
+
+****************
+Merging Elements
+****************
+
+This functionality allows to merge coincident elements of a mesh. Two elements are considered coincident if they are based on the same set of nodes.
+
+.. image:: ../images/mergeelems_ico.png
+ :align: center
+
+.. centered::
+ *"Merge elements"* menu button
+
+To merge elements choose in the main menu **Modification** -> **Transformation** -> **Merge elements** item. The following dialog box shall appear:
+
+.. image:: ../images/mergeelems_auto.png
+ :align: center
+
+.. |ad| image:: ../images/add.png
+.. |rm| image:: ../images/remove.png
+.. |mv| image:: ../images/sort.png
+
+In this dialog:
+
+ * **Names** contains names of the selected mesh objects whose elements will be merged.
+ * **Automatic** or **Manual** Mode allows choosing how the elements are processed. In the **Automatic** Mode all elements created on the same nodes will be merged. In **Manual** mode you can adjust groups of coincident elements detected by the program.
+ * **Exclude groups from detection** group allows to ignore the elements which belong to the specified mesh groups. This control is active provided that the mesh includes groups.
+ * **Elements to keep during the merge** group allows to specify elements to keep in the mesh. (By default an element being the first in a group of coincident elements is kept.) It is possible to either select elements in the Viewer or select groups whose elements will be kept.
+
+ * *Selection* button activates selection of elements to keep.
+ * **Elements** button activates selection of elements in the Viewer.
+ * **Groups and sub-meshes** button activates selection of groups and sub-meshes.
+ * **Add** button adds selected elements or groups to the list.
+ * Elements or groups selected in the list can be removed using **Remove** button.
+
+
+ If the **Manual** Mode is selected, additional controls are available:
+
+ .. image:: ../images/mergeelems.png
+ :align: center
+
+
+ * **Detect** button generates the list of coincident elements found in the selected object.
+ * **Coincident elements** is a list of groups of elements for merging. After the operation all elements of each group will be united into one element. The first element of a group is kept and the others are removed.
+ * **Remove** button deletes the selected group from the list.
+ * **Add** button adds to the list a group of elements selected in the viewer with pressed "Shift" key.
+ * **Select all** check-box selects all groups.
+ * **Show double elements IDs** check-box shows/hides identifiers of elements of the selected groups in the 3D viewer.
+ * **Edit selected group of coincident elements** list allows editing the selected group:
+
+ * |ad| adds to the group the elements selected in the viewer.
+ * |rm| removes the selected elements from the group.
+ * |mv| moves the selected element to the first position in the group in order to keep it in the mesh.
+
+
+
+ * To confirm your choice click **Apply** or **Apply and Close** button.
+
+
+In the following picture you see a triangle which coincides with one of the elements of the mesh. After we apply **Merge Elements** functionality, the triangle will be completely merged with the mesh.
+
+.. image:: ../images/meshtrianglemergeelem1.png
+ :align: center
+
+**See Also** a sample TUI Script of a :ref:`tui_merging_elements` operation.
+
+
