That it is still used as a sheep pen is part of what makes it interesting. The wall, roughly a metre thick and standing about 1.3 metres high, was rebuilt in drystone, the traditional technique of stacking stone without mortar, but it appears to have been raised on the foundations of something considerably older. The present structure and the ancient one beneath it have become, in a sense, the same object.

The enclosure measures approximately seven metres east to west, with its straight side running eight and a half metres along the eastern edge, giving it that distinctive flat-backed D shape. A narrow entrance, just under a metre wide, opens at the north-east. To the south, the remains of an old field wall run up and abut the enclosure directly, suggesting this was once part of a broader pattern of land division in the valley. Whether the original enclosure was built for livestock, for protection, or for some other agricultural purpose is not recorded, but its position at the head of a remote bog valley, on ground that has clearly been worked and divided for a long time, hints at a farming landscape with deep roots.