<li>Select a mesh (and display it in the 3D Viewer if you are going to
pick elements by mouse).</li>
<li>In the \b Modification menu select the <b>Union of triangles</b>
<li>Select a mesh (and display it in the 3D Viewer if you are going to
pick elements by mouse).</li>
<li>In the \b Modification menu select the <b>Union of triangles</b>