It is classified as an inland promontory fort, a form of defended enclosure that uses natural topography rather than the sea cliffs more commonly associated with the type. What makes this particular example quietly puzzling is how little of the expected defensive architecture survives, or perhaps ever existed.

A promontory fort typically works by cutting off a naturally projecting piece of high ground with an artificial bank and ditch, creating an enclosed space that requires defence on only one or two sides. Here, on the southern flank of the outcrop, there is a wide fosse, a flat-bottomed trench or ditch, running between 13 and 15 metres across at its top and dropping to a depth of around six metres. It extends westward for roughly 100 metres as far as a public road. The difficulty is that this impressive feature may be entirely natural in origin, and there is no evidence of a constructed earthwork bank accompanying it. The outcrop shares its classification with Duncormick castle, which occupies the same site, suggesting a long continuity of use for a piece of ground that clearly held strategic value in the valley of a small north-south stream. A house now occupies part of the promontory, further complicating any reading of the original layout.