Various bits of PHP / HTML to customize this theme.

1. Change nav menu to full width, always open

In the skin editor you can click the gear beside the "Primary Navigation" container and change the HTML class to "nav-primary active" on one of the templates.

Then add CSS like this to your Thesis Custom CSS:

.site-header {top: 40px;}
.toggle-menu {display: none !important;}

If you don't want to have a floating menu (which is less likely to cause issues) use this instead:

.navigation {position: relative;}
.toggle-menu {display: none !important;}