This crude stone monument measures half a metre in height and widens from 17 centimetres at its base to 22 centimetres where the arms extend. Carved from local stone and aligned along a north-south axis, it represents the kind of simple devotional markers that once dotted the Irish countryside, serving as waymarkers, boundary stones, or memorials.

The most distinctive feature of this cross-slab appears on its eastern face, where an uncomplicated Latin cross has been carved into the weathered surface. Unlike the elaborate high crosses found at major monastic sites, this humble monument reflects the grassroots nature of early Irish Christianity; simple, locally made markers that served the spiritual needs of rural communities. The choice to carve the cross on the eastern face follows Christian tradition, as east was considered the direction of resurrection and renewal.

This particular cross-slab was documented during the comprehensive Archaeological Survey of County Donegal, compiled by Brian Lacey and his team in 1983. The survey catalogued field antiquities spanning from the Mesolithic period through to the 17th century, preserving crucial information about monuments that might otherwise be overlooked or forgotten. While it may lack the grandeur of more famous Irish crosses, this Drumnasillagh stone offers an authentic glimpse into how Christianity was practised and commemorated at the local level throughout rural Ireland.