The stone is a cross-slab, carved with a delicate and unusual design, and it was only identified in August 2015, when a photographic survey of the underground passage in which it sits finally brought it to light.

The passage in question is a souterrain, an underground stone-lined tunnel of the kind built throughout early medieval Ireland, typically for storage or refuge. This particular souterrain at Townplots contains a narrow east-west drystone passage, just 55 centimetres wide and 78 centimetres high, and somewhere in its construction the builders incorporated the cross-slab as a roof lintel, with both ends of the stone slotted into the side walls and hidden from view. The carving itself faces downward into the passage. It shows a stylised cross rendered in false relief, meaning the design is defined by incised grooves rather than being raised above the surface. A grooved shaft, tapering slightly toward its top, rises to pierce a grooved circle roughly 16 by 14 centimetres across. Four linear grooves radiate outward from the top of the shaft, dividing the interior of the circle into five roughly equal triangular sections that wrap around the shaft like the petals of a flower. Each of those five segments contains a small circular dimple at its centre, with two further dimples cut into the shaft itself, one at the top and one at the base. The total length of the cross, as visible, is 24 centimetres, though two parallel vertical grooves rising from the top of the circle suggest the carving continues into the section of stone now buried within the north wall of the passage. One segment of the circle, on the upper west side, shows surface damage, and it is possible that this existing flaw gave the souterrain's builders their justification for recycling what had presumably once been a devotional or commemorative object into plain structural use.