The slab, measuring roughly 74 centimetres long and 53 centimetres high, is an end panel from an altar tomb, the kind of raised chest-like monument that was common in late medieval Irish ecclesiastical settings. It currently sits at the western end of a Cantwell/Butler altar tomb dated to 1528, positioned in the eastern recess of the south wall of the chancel, though this is almost certainly not where it began its life.

The carving depicts three apostles, each standing within a semi-circular niche separated by twisted columns. St James the Major is the most elaborately detailed: a scallop shell in his hat (a pilgrim badge associated with the shrine at Santiago de Compostela in Spain), a travelling staff in his left hand, a book in his right, and a purse at his belt. Beside him stand St Andrew, identified by his saltire cross, and St Peter, holding two keys in his right hand and a book in his left. According to art historian John Hunt, the figures most likely date from the second half of the sixteenth century and show the hand of the O'Tunney workshop, a Kilkenny-based school of stone carvers responsible for some of the finest ecclesiastical sculpture in late medieval Ireland. Two details, however, mark this slab as unusual even within that tradition: the twisted columns supporting semi-circular arches are not characteristic of the workshop's known output, and the three saints appear in the reverse of their conventional order, a small but telling deviation that suggests either a particular commission or a lapse in the standard compositional formula.