It sits embedded horizontally into the upper surface of the wall, slightly proud of the stonework around it, broken into three pieces and patched with cement. What makes it quietly remarkable is the inscription running along its northern edge: a line of ogham, the early medieval Irish script that uses a series of notches and strokes carved along a central stem line, typically found on standing stones rather than repurposed as rubble in a church wall.

The stone measures 1.5 metres in length, 0.7 metres in width, and 0.18 metres in thickness. It was at some point incorporated into a rebuilt section of the chancel wall, flanked by a crucifixion plaque to its east and an architectural fragment to its west. The inscription has attracted some scholarly disagreement. R.A.S. Macalister, whose 1945 corpus of ogham stones remains a foundational reference, read the text as BRRUANANN. Damian McManus, writing in 1997, offered a different reading: BRRENANN. Both versions suggest a personal name, possibly a variant of Brendan, though the damaged condition of the stone leaves room for interpretation. The stone has since been documented as part of the Ogham in 3D project run by the School of Celtic Studies at the Dublin Institute for Advanced Studies, which uses photogrammetry and three-dimensional modelling to record inscriptions that centuries of weathering and mishandling have made difficult to read with the naked eye.

Aghadoe is an early ecclesiastical site with a long history of structural change and reuse, and the ogham stone embedded in its chancel wall is a good example of how older monuments were routinely cannibalised for later building projects. The inscription faces upward as the stone now lies, but it was carved for a stone that once stood upright. Visitors to the site can see the stone in situ, though its position within the wall means the ogham scoring along its edge requires some patience to locate and read.