What makes it worth a second look is how it was built: the straight side of the D is not a constructed wall at all, but simply the exposed face of an outcropping rock, pressed into service as a ready-made boundary. The curving wall that completes the shape is made from stone slabs set at right angles to the line of the wall, each leaning against its neighbour, a technique that gives the structure its character even in its partially collapsed state. The wall still stands to around 0.75 metres in height, with a thickness of roughly 0.55 metres, and the interior, though scattered with rubble, remains more or less level.

Hut sites of this kind are the physical traces of early settlement in the Irish landscape, often associated with seasonal occupation or agricultural activity, and frequently found on hillsides where land was marginal rather than intensively farmed. The Foilakilly example measures 2.45 metres on its northwest to southeast axis, which gives a sense of just how modest a space it enclosed. The builders worked with what the hillside offered, using the natural rock as one wall and constructing only what was necessary around it. Roughly 40 metres to the southwest, a second hut site survives, suggesting this was not an isolated presence on the hillslope but part of a small cluster of activity, whatever its date or purpose.