
the second <strong>AIR</strong> command in the listing, the dummy surface would not
  have been inserted as surface 1. To fix that, simply type:</p>

<p><strong>
    U L<br>
    INS 1<br>
    EOS<br>
</strong></p>

<p>If you had typed three <strong>AIR</strong> commands instead of
two <strong>AIR</strong> commands near the top of the input command
list, you would now have surface 1 and surface 2 as dummy surfaces. To
remove surface 2, just type:</p>

<p><strong>
    U L<br>
    DEL 2<br>
    EOS<br>
</stro