Test Case Boilerplate
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HTML
<script src="http://code.jquery.com/ui/jquery-ui-git.js"></script>
<link rel="stylesheet" href="http://code.jquery.com/ui/jquery-ui-git.css">
<ul>
<li>menu 1
<ul>
<li>submenu 1<ul></ul></li>
<li>submenu 2<ul></ul></li>
</ul>
</li>
</ul>
JavaScript
$('ul').sortable({connectWith: "ul"});