It measures roughly a metre across, its edges bevelled, and at its centre a small rectangular socket has been cut into the upper surface, just deep enough to have once gripped the base of a standing cross. The cross itself is long gone, and what remains is essentially a socket waiting for something that will never return.

The 1837 edition of the Ordnance Survey six-inch map already marks this spot simply as "Site of Cross", which suggests the shaft had been lost well before the nineteenth century. A survey visit in June 1981 recorded a broken cross base on a low mound to the south-west of the church, though that particular fragment could not be located in subsequent inspections, leaving only the limestone socket-stone still standing. The socket itself is modest in scale, measuring 0.27 metres by 0.17 metres and just 0.1 metres deep, dimensions that speak to a shaft of moderate size rather than any great monumental cross. Such free-standing crosses, common across early medieval Irish ecclesiastical sites, typically marked sacred boundaries, processional routes, or burial grounds of particular significance. At Tristernagh, with its history as an Augustinian priory site, a cross of this kind would have been a functional part of the religious landscape rather than purely decorative.