It had been reused as a structural lintel above the west door of Kilgobbin Church, near Stepaside Village on the northern slope of Three Rock Mountain in County Dublin, and when the porch wall shifted and the doorway was eventually blocked up, the stone simply disappeared into the building. A considerable amount of limewash had accumulated on its decorated face by the time anyone thought to look.

The slab only came to light in 1983, when Dublin County Council undertook conservation works at Kilgobbin church and graveyard. Described in detail by Ó hÉailidhe in 1984, it belongs to the Rathdown Group, a collection of Early Christian grave-slabs found across south County Dublin and dated to the Viking period. The slab is cut from granite and measures 1.6 metres long, tapering from 46 to 41 centimetres in width, with a rounded narrower end. Its decoration, incised into one face only, consists of diagonal lines running from corner to corner to form a saltire, the X-shaped cross sometimes called St Andrew's Cross or Crux Decussata, with a further vertical line running down the centre of the slab and a shallow cup-mark at the point where the arms of the cross meet. Together, these elements may be read as a Christogram: the vertical line paired with the diagonal X represents the Greek letters I and C, an abbreviation for the name of Jesus Christ, making the whole composition function something like the better-known Chi Rho symbol. Possible traces of a loop or circle and additional lines are visible on the stone's surface. Related slabs with comparable motifs, sometimes combined with herringbone patterns or cup marks, have been recorded at Rathfarnham and Whitechurch. The Kilgobbin slab is now fixed to the internal face of the northern wall of the ruined church, which stands at the centre of the graveyard.

Kilgobbin graveyard sits just off Kilgobbin Lane near Stepaside, and the ruined church is accessible from the lane. The slab is mounted inside the church ruin, so it is worth stepping through the walls to find it on the north face. The incised lines are relatively fine and can be easier to read in low, raking light, which picks out the shallow grooves in the granite surface. A 3D model of the slab is also available online at skfb.ly/oFGIM for anyone who wants to examine the decoration in detail before or after a visit.