It is easy to walk past without noticing it. The slab is slightly tapered, measuring around 1.6 metres in length and between 0.4 and 0.65 metres wide, with a bevelled edge running all around its perimeter. Carved across its surface in false relief, a technique in which the background is cut away to leave the design proud of the stone, is a cross with an elaborate floriated head, meaning the arms terminate in decorative leaf or flower forms. The shaft is slim, rising from a stepped base. There is no inscription, so whoever lies beneath has no name here.

Canon Island takes its name from the Augustinian canons who established a house there during the medieval period, and the church interior that shelters these slabs belongs to that monastic complex. A second medieval graveslab also survives on the island, lying flat beneath the east window of the same church, a quiet companion piece to the one beneath the sedilia. Together they are among the more tangible traces of the individuals who lived and died within this remote island community, whose daily life would have been shaped by the tidal rhythms of the Shannon and the disciplines of monastic rule.