What looks at first like a single defensive system turns out, on closer inspection, to be at least two phases of construction laid one over the other, the earlier largely buried beneath the later. A promontory fort is exactly what the name suggests: a headland made into an enclosure by cutting it off at the landward end with banks and ditches, letting the sea do the defensive work on the remaining sides. Here the main visible works are substantial, an inner bank some 53 metres long and an outer bank stretching to 91 metres, with a fosse, or ditch, between them and a causeway crossing it at the entrance.

The more intriguing detail lies beneath. Researcher Katharine O'Conor, writing in 2003, identified traces of two smaller, earlier ditches at the southern end of the site, apparently cut through by the larger earthworks visible today. This stratigraphic relationship suggests that the imposing banks seen now are secondary, built over an older, more modest enclosure. O'Conor proposed that the large-scale refortification may have been carried out by Raymond le Gros in 1170, in preparation for an assault by the Ostmen of Waterford and their Irish allies. Raymond le Gros was one of the early Anglo-Norman commanders who arrived in Ireland in the years around the invasion of 1169 to 1170, and the timing would fit the turbulent military activity along the Wexford and Waterford coastline during that period. An antiquarian note from Westropp in 1906 also recorded a low rectangular raised feature inside the enclosure, measuring roughly 6.4 by 4.7 metres, which may represent the footprint of a former hut. The fort sits within a broader promontory, itself defended on its landward northern side by a separate linear earthwork, suggesting that the defensive thinking here operated at more than one scale.