Poulanaffrin and Clashanaffrin, the hole and the trench of the mass, are what local people called a disused quarry on a hillside in County Limerick where, during the Penal Laws, Catholic congregations gathered in secret to attend Mass. The Penal Laws, a series of statutes enacted from the late seventeenth century onward, severely restricted Catholic worship in Ireland, pushing priests and their congregations out of doors and into the landscape. Quarry hollows, natural depressions, and remote hillsides became functional places of worship, and the names people gave them became a form of communal memory.

Writing in 1909 to 1911, a historian named Lynch recorded that Mass had been attended at this spot during penal times. The Ordnance Survey Name Books, compiled in the nineteenth century as part of a systematic effort to document Irish placenames and their physical surroundings, described the site as a small pit roughly two chains in diameter, about fifteen feet deep, set into the face of a hill and ringed by a few hawthorn bushes. Two chains is approximately forty metres, which gives a sense of the scale; this was not a crevice but a proper hollow, capable of holding a gathering. The quarry that formed it has long since been filled in, and what survives today is a pair of conjoined shallow depressions running roughly fifty metres on a northwest to southeast axis, with a depth of around one and a half metres. A face of limestone rock remains visible from the northeast.

The site sits close to the summit of a hill in Inch St. Lawrence North, on a northeast-facing slope in rolling pasture. Because the depressions are shallow and the ground is open farmland, the feature is easy to miss unless you are specifically looking for it. The exposed limestone face on the northeast side offers the clearest visual marker from a distance. The hawthorn bushes noted in the Ordnance Survey records may still be present in some form, and hawthorn has long been associated in Irish tradition with sacred or liminal ground, which adds a quiet layer of meaning to their presence here. There is no formal access infrastructure, and visiting would require crossing private agricultural land, so seeking local permission beforehand is advisable.