The Scent Border isn't an actual geographical feature; it's more of a territorial marking placed around the edge of the Mouse Territories manufactured by the mice in order to ward off predators. Many mice don't even know of the Scent Border's existence, and only a few living mice have ever gone beyond its boundaries. With the help of the scientists at Sprucetuck, the Scent Border is repoured at least twice a year. This is one of the most vital duties of the Mouse Guard, therefore its execution is placed into the paws of only the most trusted patrols.
Border between the Mouse Territories and Open Country.