It is a C-shaped structure, about 36 metres long, built from posts and wattle, the woven network of branches and rods that was among the most practical and widespread building materials available before industrialisation. The mouth of the weir faces upstream, a deliberate orientation designed so that fish travelling with the ebbing tide would be funnelled into the enclosure and left stranded as the water retreated. It is a low-tech trap of considerable ingenuity, and its basic logic has barely changed across centuries of use on Irish estuaries.

The weir dates to the post-medieval period, a broad designation covering roughly the sixteenth century onwards, when fish traps of this kind remained a routine feature of tidal life along major waterways. Archaeologist Aidan O'Sullivan documented the structure in July 2000, recording its dimensions and orientation as part of wider research into intertidal and foreshore heritage along the Shannon. The weir sits on the west bank of the creek, its C-shape oriented east to west, and its placement on the upper foreshore means it would have operated in the shallower, more marginal zone where the tide's retreat is most pronounced. Such structures are easily overlooked, partly because they lie in the intertidal zone and are only exposed at low water, and partly because their materials, being organic, tend to survive in fragmentary form rather than as dramatic upstanding remains.