The enclosure is oval, measuring roughly 22 metres east to west and 15 metres north to south, and it is defined not by a single wall but by two concentric stone spreads separated by a fosse, the term for the ditch or hollow cut between defensive walls. That outer spread stands nearly a metre high on its exterior face at the south-east, while the inner wall rises to almost three metres on the outside at the same point, giving a sense of how substantial the original construction must have been before centuries of collapse and vegetation took over.

What makes the arrangement particularly interesting is the question of how people actually entered. There is a well-defined causewayed entrance, roughly four metres wide, on the western side, where a raised pathway crosses the fosse. A causewayed entrance of this kind was a deliberate feature, controlling movement and making approach visible. Yet a narrower gap, about two metres wide, cut through both walls at the south-south-east may represent the older original entrance, later superseded by the more formal western one. The fort also has an unusual relationship with water: the source of a northward-flowing stream lies just to the east and runs into the fosse in the north-east, which is precisely where the outer wall disappears entirely, as though the builders incorporated the stream as a natural barrier in place of the stonework. Michael J. Moore's Archaeological Inventory of County Leitrim, published in 2003, provides the detailed measurements on which this account is based.