A demo of ruler plug-in at body level

jQuery, CSS and HTML
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<link href="css/jquery-ruler/ruler.css" rel="stylesheet" type="text/css">
<link href="css/jquery-ruler/demo.css" rel="stylesheet" type="text/css">
</head>

<body>
<h3>A Demo of Ruler plug-in</h3>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>


<script src="js/jquery-ruler/jquery.ruler.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/modernizr/2.6.2/modernizr.min.js"></script>
<script>
$(function() {
  $('body').ruler();    
});
</script>

</body>
</html>