Below it, a bilingual plaque records simply that Mass was said here in Penal times, which is perhaps all the explanation needed. The site is a rock platform on the eastern bank of the river, with the cliff rising behind it, the kind of naturally sheltered outdoor space that congregations relied upon when the public practice of Catholicism was effectively outlawed.

The Penal Laws, a series of legislative measures introduced in Ireland following the Williamite wars of the late seventeenth century, stripped Catholics of property rights, access to education, and the freedom to worship openly. Priests who celebrated Mass could be arrested, and so communities adapted, gathering at remote locations, often natural features like boulders or cliff-sided riverbanks, to receive the sacraments out of sight. These sites became known as mass-rocks, and hundreds survive across Ireland, ranging from simple flat stones in open fields to more sheltered positions like this one at Chimneyfield, where the cliff would have offered both concealment and a degree of acoustic shelter. The cross and plaque here are a later addition, a deliberate act of commemoration rather than a survival from the period itself, though the rock platform and its setting are the genuine article.

The site is reached from the south via a path that leads north from the road, or from the west by crossing an iron and wooden bridge over the river Bride. The cross, visible against the cliff face, serves as a fairly reliable landmark once you are in the vicinity.