<li><b>In Place of Second Shape</b> restricts the range of accessible
elements to those sub-shapes of the Main Shape that geometrically
coincide with the <b>Second Shape</b>.</li>
-<li><b>Sub-Shapes of Second Shape</b> restricts the range of accessible elements to
-those sub-shapes of the Main Shape that are sub-shapes of <b>Second
-Shape</b>.</li>
+<li><b>Sub-Shapes of Second Shape</b> restricts the range of
+accessible elements to those sub-shapes of the Main Shape that
+are sub-shapes of <b>Second Shape</b>. This is useful because
+sometimes purely geometrical coincidence is not enough and it
+is necessary to work with shapes, which actually belong both
+to the main and the second shape.</li>
</ul>
<li> You can select the elements of your group in two ways:
<ul>
