Clarifying bearer security scheme

I've been trying to understand how `bearer auth.` -independent of `oauth`- works and can be implemented. Unfortunately, I could neither find a broad explanation (had a look at the [TD documentation](https://www.w3.org/TR/wot-thing-description/#bearersecurityscheme)) nor a concrete example; leaving me with question marks on my mind. It would be great if somebody could supply a sample `thing` and `consumer` pair so as to show the implementation details and how things work.

Thanks in advance.