A rath is an early medieval ringfort, typically a raised earthen enclosure that once defined a farmstead and its immediate territory, and this one at Knockbrack still retains a substantial curving bank on its south-western to east-south-western arc, rising between 1.7 and 2 metres on its outer face. Beyond that bank lies a fosse, the defensive ditch that accompanied such enclosures, roughly 3.4 metres wide. The straight southern edge of the site, however, is simply a scarp and hedgerow where the main road sliced through, and a further by-road on the eastern side has eaten into both the fosse and the outer bank. Hawthorn and hazel ring the surviving perimeter, and long grass and brambles cover much of the interior, where local tradition holds that a souterrain, an underground stone-lined passage associated with storage or refuge, lies concealed beneath.

The nineteenth-century roads that bisected the site did lasting damage, but twentieth-first-century infrastructure came close to doing worse. In 2007, road-widening works on the eastern side broke into the fosse before being halted. Mitigation excavations carried out under archaeological supervision in 2008 recorded the exposed section and investigated a drainage trench cut across the minor road. Within that trench, a layer of burned or baked clay, roughly 1.9 metres across and 0.8 metres deep, was uncovered alongside what appeared to be heavily burnt sandstone. The feature contained no objects or datable material, but the supervising archaeologist, Morahan, suggested it likely represents part of a fosse that may have belonged to a conjoined element of the rath, raising the possibility that the original enclosure was more complex in plan than what survives above ground. Separately, testing to the west of the site in advance of pipe-laying for a local water scheme produced nothing of archaeological note.