It is a jambstone, part of what would once have been a door or window opening, chamfered along its edge at a precise angle to ease the transition between the frame and the surrounding stonework. Measuring 0.70 metres by 0.26 metres, with a plain stop where the chamfer terminates, it is the kind of architectural detail that speaks to careful, considered building. At some point, that building ceased to exist, or was altered, and the stone was pressed into secondary use as ordinary fill.

The wall in question forms the northwest boundary of St. John's graveyard in Cashel, at its junction with Ager's Lane. The graveyard surrounds St. John's Church of Ireland Cathedral, which itself occupies the site of a medieval church. The jambstone is set into the north angle of the external face of that wall, meaning it sits on the outside, visible to anyone passing along the lane rather than to those within the burial ground. Whether the stone came from the medieval church on whose footprint the cathedral stands, or from some other vanished structure in the area, is not recorded. In a town as historically layered as Cashel, where the famous Rock dominates the skyline and medieval fabric persists in unexpected corners, the supply of displaced architectural material would not have been scarce.

The stone is easy to miss precisely because it has been so thoroughly absorbed into its surroundings. Looking at the northwest corner of the graveyard wall where it meets Ager's Lane, and scanning the upper masonry, is the only way to locate it. Its chamfered profile and plain stop are the distinguishing features, the vocabulary of a craftsman working on a proper opening rather than a boundary wall, surviving here because limestone is too useful to waste.