Unused 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>
2013-12-04, original files uploaded 2009-01-29
<span class="int-own-work" lang="en">Own work</span>, based on <a href="//commons.wikimedia.org/wiki/File:BSicon_uextCONTl.svg" class="mw-redirect" title="File:BSicon uextCONTl.svg">File:BSicon uextCONTl.svg</a> &amp; <a href="//commons.wikimedia.org/wiki/File:BSicon_uextCONTr.svg" class="mw-redirect" title="File:BSicon uextCONTr.svg">File:BSicon uextCONTr.svg</a>