Yet this linear earthwork near Cornagawna, in the far north of County Leitrim, is precisely the kind of feature that rewards a second look. A fosse, in archaeological terms, is a defensive or boundary ditch, often dug in combination with the bank formed from the displaced earth. Here, the main bank runs to the south-west of the ditch, with a slighter, narrower bank to the north-east, giving the whole feature an asymmetrical profile that suggests it was designed to present a more formidable face in one direction than the other.

The earthwork sits in undulating terrain of bog and scrub, about 1.4 kilometres south of the southern end of Lough Melvin and roughly 300 metres from the Lattone River, also known as the County River, which marks the boundary between Leitrim and Fermanagh. That proximity to a historic county boundary is suggestive. Linear earthworks of this kind are often interpreted as territorial markers, stock barriers, or frontier features, sometimes of considerable antiquity, though the available record does not date this particular example precisely. The measured fosse is 4.4 metres wide and 0.7 metres deep over its recorded 100-metre length, but the feature does not end there; a related earthwork continues for approximately a further kilometre to the south-south-east, implying that what survives here is only a fragment of something originally much more substantial, running through a landscape that has since been claimed by peat and scrub vegetation.