Floating contents menu?

Hi,

I've installed T3 on a new installation of Joomla 3 and I'm loving it.

One of the features I really want to to is the floating contents menu on the right hand side of the following page:

http://t3-framework.org/documentation/layout-system.html

I really like how it highlights which section of the page you're reading as well as acts a menu for the page.

I've spent the evening trying to figure out how to do this, but I'm still clueless - please could you explain for me?

Thanks in advance,

Paul Hughes