<ol>
<li>From the \b Modification menu choose the <b>Union of two
triangles</b> item or click <em>"Union of two triangles"</em> button
-in the toolbar.
+in the tool-bar.
\image html image71.png
<center><em>"Union of two triangles" button</em></center>
</li>
<li>Enter IDs of nodes forming the required edge in the \b Edge field
- (the node IDs must be separated by a dash) or select this edge in
+ (the node IDs must be separated by dashes) or select this edge in
the 3D viewer.</li>
<li>Click the \b Apply or <b>Apply and Close</b> button.</li>
</ol>