Funny that it`s called `Bringsle`in english, because here we call it `Bringsler` - very simular!
I myself don`t have a bringsle dog and the method itself is rather seldom.
Anyhow... her are some links (even in english ) to explain how it works:
http://www.northidahosearchdogs.com/nextstep.html
http://www.petjoyonline.com/PhotoGaller ... SAR%2D0019
and a german one (to enjoy the pictures )
http://www.rettungshunde.ch/rettungshunde_bringsler.htm