Fish weirs of this type work by guiding fish into an enclosed space as the tide recedes, trapping them without the need for active fishing. What makes this one quietly interesting is how much structural logic survives in so compact a structure: an L-shaped arrangement of post-and-wattle fencing, where upright stakes are woven with thin branches or rods to form a permeable but directional barrier, angled to exploit the movement of water rather than fight it.

Aenghus O'Sullivan's 2001 survey recorded the weir in detail during fieldwork carried out in July 2000. The main fence runs roughly north-north-east to south-south-west and extends 19 metres in total length, positioned about 6 metres south of a neighbouring island feature. A shorter flood fence, just 3 metres long, runs east-north-east to west-south-west, while a shore fence of 16 metres runs north-west to south-east. The two principal elements meet at an enclosed angle of approximately 90 degrees, forming the characteristic trap-corner that gives the structure its function. The construction is classified as post-medieval, placing it broadly after the sixteenth century, though post-and-wattle weir technology had been in continuous use along Irish estuaries for far longer than that. The Shannon Estuary was historically one of the more productive fishing grounds on the western seaboard, and structures like this one were a practical, low-cost means for local communities to harvest salmon, eels, and other fish as part of everyday subsistence.