title: Template Inheritance in Nunjucks, what are the requirements?
body: <p>Ok super basic question but I must be missing something.</p>
  
  <p>I render my page:</p>
  
  <pre><code>router.get('/', function(req, res) {
          res.render('index.njk', {});
  });
  </code></pre>
  
  <p>Create my base layout, main-layout.njk in layout folder:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  
  &lt;html&gt;
      &lt;body&gt;       
          {% block content %}
          {% endblock %}   
      &lt;/body&gt;  
  &lt;/html&gt;
  </code></pre>
  
  <p>Extend my template, index.njk to add content to the layout:</p>
  
  <pre><code>{% extends 'layout/main-layout.njk' %} 
  
  {% block content %}
  &lt;?php include_once("analyticstracking.php") ?&gt;
  &lt;main&gt;
  
     &lt;p&gt;sploooge&lt;/p&gt;
  
     {% block panel %}{% endblock %}
  
  &lt;/main&gt;
  {% endblock %} 
  </code></pre>
  
  <p>Now I would like index.njk to be extended by panel.njk (the file is in the same folder):</p>
  
  <pre><code>{% extends 'index.njk' %} 
  
  {% block panel %}
      &lt;p&gt;second sploooge&lt;/p&gt;
  {% endblock %} 
  </code></pre>
  
  <p>But I cannot get it to appear. The documentation doesn't mention anything but do I need to render it somehow like index.njk?</p>