Its walls, built without mortar in the drystone tradition, still stand to around 1.3 metres in places, and a heap of rubble at the eastern end is thought to be the remnant of a collapsed gable. What makes this unassuming structure quietly significant is its purpose: local tradition holds that it served as a mass-house during the Penal era, a time when Catholic worship was suppressed by law and congregations gathered in remote or concealed locations to receive the sacraments.

The Penal Laws, enforced with varying degrees of rigour from the late seventeenth century onwards, effectively banned Catholic clergy from ministering openly in Ireland. In response, communities adapted whatever shelter they could find, sometimes a farmhouse, sometimes a hollow in open ground with a flat rock for an altar, and sometimes a purpose-built structure kept deliberately inconspicuous. The building at Carks fits that pattern well. It measures roughly 13.7 metres east to west and only 3.8 metres north to south, a narrow footprint that would not have drawn much attention in the landscape. Inside, a cross wall divides the space into two compartments: a larger room at the eastern end, about 8.8 metres long, with a doorway of 0.8 metres width in the north wall, and a smaller western room measuring around 4 metres. The larger eastern chamber was most likely the worship space, with the smaller room perhaps serving a functional or vestry-like role, though this is speculation based on the layout rather than documented record.

The site lies in rough pasture and is covered by dense vegetation, which means it is easy to miss and not straightforward to read at ground level. The walls are substantial enough, a metre thick in places, to remain legible despite the overgrowth, but the collapsed eastern gable makes the full outline harder to trace from within. For anyone with an interest in the physical traces of religious practice under suppression, the very modesty of the structure is part of what it communicates.