In the graveyard at Castledermot, a small granite slab lies broken and face-up on the ground, easy to walk past without a second glance. It measures just 64 centimetres in length, and yet cut into its surface is a Latin cross with expanded terminals, the ends of each arm flaring outward in a style commonly associated with early medieval Irish ecclesiastical carving. The slab is recumbent, meaning it lies flat rather than standing upright, and its fractured state suggests a long and not entirely gentle history of exposure.

Castledermot, known in Irish as Diseart Diarmada, the hermitage of Diarmait, was an important monastic site from at least the ninth century, and the graveyard retains several carved stones from that period. This particular slab sits to the west of the South Cross, one of the site's well-known high crosses, which gives some sense of its position within a landscape that was once densely populated with early Christian sculpture and activity. The cross type incised on the slab, a simple Latin form with those characteristic flared terminals, was a common way of marking a grave or consecrating a surface in early medieval Ireland, and such slabs are often associated with the graves of monks or lay patrons of a monastery. The granite from which it is made is a durable local material, which likely accounts for the survival of the incised line work despite the slab's broken condition.

The slab lies close to the South Cross, so a visitor who locates that more prominent monument and then looks to the west should be able to find it without difficulty. It rewards a close look at ground level, where the incised cross becomes easier to read, particularly in low or raking light.