You can include one HTML file inside another by linking to it with an @include tag. Just drop the .html extension, and include it like this:
Hammer will find your _header.html file, and render its content in place of the tag. If you included _header.html in index.html, when you viewed that same index.html file in your Build folder you’d see it would also contain the markup from _header.html.
You can use as many includes as you want, and you can even include files within includes. Be careful, though - don't include your templates into a loop!
