It is a substantial slab, roughly 1.63 metres long and 0.6 metres wide, lying south of the south-east angle of the nave. What makes it worth stopping for is not its size but what is carved into its face: a latin cross formed from six incised lines, arranged into four panels within a two-line frame, with a circle at the centre and half-circles at each extremity. The geometry is precise and purposeful, the kind of decorative cross-carving that became a quiet tradition on early medieval Irish grave markers. The surface, however, has scaled away badly over time, and the carving that remains is worn close to illegibility.

The stone carries more than ornament. R.A.S. Macalister, examining it in the late 1940s, identified a fragmentary inscription running alongside the cross, so eroded that only partial letters survive. What can be reconstructed reads roughly as OROIT DO, the opening of a formula common on early Irish memorial stones, meaning a prayer request: "a prayer for" someone, whose name follows. The surviving portion of the name has been tentatively read as ending in something like DOMNOGG, though the middle section is lost entirely. The formula itself is well attested across early Christian Ireland, where carved slabs frequently asked passers-by to offer a prayer for the named individual, functioning as a kind of perpetual intercession worked into stone. H.G. Leask had noted the slab earlier, in 1950, describing the cross design in detail but apparently without comment on the inscription's legibility. A drawing of the slab was included in Robert Cochrane's record of the ecclesiastical remains at Glendalough, published in 1925 as part of the Eightieth Annual Report of the Commissioners of Public Works in Ireland, which gives some sense of how the surface appeared in the early twentieth century, before further weathering took its toll.