The earthen bank that once traced a rough circle across this ground has been worn down over centuries to little more than a suggestion in the grass, and along one arc, from the south-east to the south-south-west, even that suggestion has disappeared entirely. What survives is a subcircular form measuring roughly 62 metres east to west, enough to give a sense of the original scale, though the effort of picturing it requires some imagination.

Enclosures of this type, typically formed by a raised earthen or stone bank enclosing a roughly circular area, are among the most common field monuments in Ireland, and also among the least understood in their particulars. They served a range of purposes depending on period and context, from settlement enclosures associated with early medieval farmsteads to stock enclosures of various dates. At Knockogonnell, the bank has been further altered by the landscape working around and through it: a field boundary cuts across the section where the surface trace has already been lost, and a road runs close to the western side of the monument. A gap about six metres wide in the western bank appears to be a modern insertion rather than an original entrance.

The straightening of the bank at the south-east corner is a telling detail, the kind of quiet pragmatic adjustment that happened when farmers needed a boundary to behave like a straight line rather than an ancient curve. Taken together, these modifications paint a familiar picture of an old monument gradually absorbed into a working agricultural landscape, its original outline surviving only in the portions that happened to be inconvenient to remove.