The site is a rath, the Irish term for a ringfort, which was the most common form of rural settlement in early medieval Ireland, typically enclosing a farmstead and its associated structures within an earthen bank and ditch. This one at Kilgarriff is quietly companionable: another rath of the same type sits roughly 150 metres to the west, along the same ridge spine, suggesting that whoever chose this ground understood it well enough to return.

The fort measures almost exactly 29.6 metres north to south and 29.5 metres east to west, making it very nearly circular. Its boundary is defined partly by a scarp, a cut or step in the earth standing around 1.8 metres high on the northeast to southern arc, and partly by a low bank on the opposite side, which has been incorporated into a working field fence and now carries a post-and-wire top. That kind of layering is common across the Irish landscape, where prehistoric and early medieval earthworks were absorbed into later agricultural patterns rather than cleared away. A gap about two metres wide in the scarp to the north-northeast may be where the original entrance once stood. The interior is level and grassy, though the perimeter has been worn down in places by grazing stock and carries a scatter of thorn bushes and gorse. The position on the ridge break gives long views to the south-southwest and north, a quality that would have mattered both practically and socially to whoever enclosed this space.