It is easy to overlook, the kind of structure that registers at first glance as simply another drystone feature in a landscape full of them. But its subcircular shape, its carefully incorporated annexe, and the presence of a second enclosure roughly 27 metres to the south suggest something more deliberate than a casual field boundary.

The enclosure measures approximately 11 metres north to south and 8.5 metres east to west internally, with the wall standing at its tallest, around 1.1 metres, at the north-east. A small annexe, barely 3.4 metres by 1.5 metres, is built into the eastern side of the main structure. Subcircular enclosures of this kind are a common monument type across Ireland, used through much of the early medieval period as farmsteads, animal enclosures, or ecclesiastical sites, though they continued to be built and reused across many centuries. At Knockbrack, the most recent chapter of the site's use appears to have been practical and unglamorous: it was probably repurposed as a sheepfold at some point, the old walls pressed into service for new livestock. Field walls radiate outward from the structure at the north-east and south-east, suggesting it was once integrated into a broader pattern of land management. Nearby, the ground is marked with lazy beds, the long parallel ridges left by spade-cultivation of potatoes or other crops, indicating that this low-lying riverside strip was once actively farmed rather than left as rough pastureland as it is today.