Many modern mobile websites have adopted a similar style of navigation. Specifically, an icon with 3 horizontal lines.

The Xara website http://www.xara.com/us/web-designer/features/ uses this style (when viewed on a smaller screen).

Further, when opening, it looks like a full-width vertical accordion.

I have not seen this style in any of the Xara templates.

Does anyone know how to replicate this?