Continuation in tunnel backward, rotated across, set "u"
<a href="//commons.wikimedia.org/wiki/User:YLSS" title="User:YLSS">YLSS</a>, original author: <a href="//commons.wikimedia.org/wiki/User:Sameboat" title="User:Sameboat">Sameboat</a>
2013-12-02, original file uploaded: 2008-12-23
<span class="int-own-work" lang="en">Own work</span>, based on <a href="//commons.wikimedia.org/wiki/File:BSicon_utCONTl.svg" class="mw-redirect" title="File:BSicon utCONTl.svg">File:BSicon utCONTl.svg</a> &amp; <a href="//commons.wikimedia.org/wiki/File:BSicon_utCONTr.svg" class="mw-redirect" title="File:BSicon utCONTr.svg">File:BSicon utCONTr.svg</a>