The feature is not visible to anyone walking the field; it only reveals itself from above, where aerial imagery picks out the soilmark of a fosse, the term for a defensive or boundary ditch, running in a ring between two and four metres wide. That kind of circular earthwork is a familiar enough form in the Irish landscape, associated broadly with early medieval settlement, though without excavation it is impossible to say precisely what this one was or who made it.

What makes the Knock enclosure particularly telling is not what it once was, but what happened to it recently. Aerial imagery from April 2015 showed an overgrown bank still curving along the northern edge of the site, running roughly northwest to northeast. That curve suggested one of two things: either a later field boundary had been built to incorporate part of the pre-existing enclosure, bending to follow its line, or it had been laid out deliberately to avoid disturbing what was already there. Either way, there was something still above ground to be avoided or reused. By March 2016, less than a year later, a subsequent image told a different story. The site had been cleared, the feature levelled, and the associated field boundaries removed along with it. What the 2015 imagery had captured was, in effect, the last recorded view of something still partially standing.