Examples
parent.tpl
<html>
<head>
<title> Page Title</title>
</head>
<body>
<slot>
</body>
</html>
child.tpl
{% layout "parent.tpl" %}
<h1>Hello</h1>
{% endlayout %}
The result would look like
<html>
<head>
<title>Page Title</title>
</head>
<body>
<h1>Hello</h1>
</body>
</html>