A rath, as these enclosures are broadly known, was typically a circular or sub-circular earthen enclosure used as a farmstead during the early medieval period, roughly the fifth to the twelfth centuries. What makes the Knockreagh example worth noting is its scale and the survival of multiple concentric banks, which place it in a category associated with higher-status settlements.

The site is multivallate, meaning it was originally enclosed by more than one bank and fosse, a fosse being the accompanying ditch from which the bank material was dug. Three such elements are distinguishable here. The outermost bank stands 1.8 metres above the surrounding ground level and 1.2 metres above its fosse. Inside that, the middle bank rises to 2.1 metres above the outer fosse and 1.8 metres above the inner one. The interior itself survives as a raised platform roughly 1.7 metres above the inner fosse. The overall external diameter stretches to 68 metres north to south and 73 metres east to west, making the whole enclosure considerably larger than the more common single-banked ringfort found across the Irish countryside. A possible entrance survives to the east, narrowing slightly as it passes through the successive banks, from 1.2 metres wide at the outermost bank to 1 metre at the inner. The best-preserved arc runs from the north-east, around through the east, and down to the south-east, with only a short stretch to the west also intact. The trackway that clips the north-western sector has pulled the symmetry off, but enough of the concentric earthworks remain on the eastern side to give a clear sense of the original form.