The remains form just two sides of what may once have been a small rectangular structure, its eastern and southern edges still traceable as stone courses roughly a metre wide and barely forty centimetres high. The other sides would have been provided by the cashel wall itself, a common enough arrangement in early Irish stone enclosures, where interior space was divided and reused across generations.

A cashel is a roughly circular dry-stone enclosure, the Irish equivalent of what might elsewhere be called a ringfort, and was typically used as a defended farmstead during the early medieval period. The interior of Cahermackirilla follows this pattern, with the smaller structure occupying the north-western sector of the enclosed space. The internal dimensions, running approximately nine metres east to west and eight metres north to south, suggest something functional rather than domestic in any elaborate sense. The most likely interpretation is that it served as an outhouse or a penned-off area, perhaps for livestock or storage, separated from the main activity within the enclosure. Nothing about the surviving fabric points firmly in either direction, and that ambiguity is part of what makes the remains quietly interesting.