Go 1.6 includes a powerful new keyword, `block`. This construct allows you to define the outer shell of your pages in a single "base" template, filling in or overriding portions as necessary.
Let's define a simple base template (`_default/baseof.html`), a shell from which all our pages will start. To find a base template, Hugo searches the same paths and file names as it does for [Ace templates]({{< relref "templates/ace.md" >}}), just with files suffixed `.html` rather than `.ace`.
<!-- Code that all your templates share, like a header -->
{{ block "main" . }}
<!-- The part of the page that begins to differ between templates -->
{{ end }}
<!-- More shared code, perhaps a footer -->
</body>
</html>
```
## Overriding the base
Your [default list template]({{< relref "templates/list.md" >}}) (`_default/list.html`) will inherit all of the code defined in the base template. It could then implement its own "main" block from the base template above like so:
```html
<!-- Note the lack of Go's context "dot" when defining blocks -->
{{ define "main" }}
<h1>Posts</h1>
{{ range .Data.Pages }}
<article>
<h2>{{ .Title }}</h2>
{{ .Content }}
</article>
{{ end }}
{{ end }}
```
This replaces the contents of our (basically empty) "main" block with something useful for the list template. In this case, we didn't define a "title" block so the contents from our base template remain unchanged in lists.
In our [default single template]({{< relref "templates/content.md" >}}) (`_default/single.html`), let's implement both blocks:
```html
{{ define "title" }}
{{ .Title }} – {{ .Site.Title }}
{{ end }}
{{ define "main" }}
<h1>{{ .Title }}</h1>
{{ .Content }}
{{ end }}
```
This overrides both block areas from the base template with code unique to our single template.
