The template provides the sticky header function (stuck to the top edge of the browser window).
Sticky header markup:
<nav id = "navigation" class = "site-header navigation navigation-justified header - sticky"> ... </header>
where id="navigation" is the unique identifier of the header;
class="site-header" - a common class for all header types;
class="header-sticky" - a unique class that is responsible for the type of header.
To activate/deactivate the sticky header function, just add remove class ".header — sticky" in header markup.