It is not especially large, measuring roughly sixty centimetres tall and forty-four centimetres wide, and it carries no elaborate knotwork, no inscription, no obvious saint's face. What it has instead is a pair of incised parallel lines, cut about eight millimetres apart, running off-centre and at a slight angle, drifting toward the edge of the slab as though the carver changed direction, or perhaps never quite finished.

A cross-slab is exactly what it sounds like: a flat stone bearing an incised or relief cross, used across early medieval Ireland as a grave marker or devotional monument. This particular example is a fragment only, which means the lines visible today are likely the surviving arm or shaft of a cross that once extended further across the stone. The positioning is precise enough to record: it sits 5.44 metres from the west gable of the nave, placed against the north wall. St. Mary's is one of several churches on Inishcaltra, a small island with a surprisingly dense concentration of early Christian remains, including a round tower and a cluster of other ecclesiastical structures that point to a community of some significance in the early medieval period. The slight diagonal of those two parallel lines, veering as they do toward the slab's edge, gives the fragment a quietly unresolved quality, as if it were caught mid-thought.