website/_includes/guide-controls.html

<div class="guide-controls">
  <hr>

  <div class="clearfix">
    {% if guide_prev %}
      <a class="btn btn-outline-primary float-xs-left" href="{{url_base}}{{guide_prev.path}}">
        &larr;
        {{i18n[guide_prev.path].title}}
      </a>
    {% endif %}

    {% if guide_next %}
      <a class="btn btn-primary float-xs-right" href="{{url_base}}{{guide_next.path}}">
        {{i18n[guide_next.path].title}}
        &rarr;
      </a>
    {% endif %}
  </div>
</div>