It is not much to look at, but this modest arrangement is the remains of a post-medieval fish weir, a type of trap known as a post alignment or creek trap, in which upright stakes were driven into the foreshore to intercept fish moving with the tidal flow. As the water receded, fish were funnelled into the narrowing gap and stranded. Weirs of this kind were once common along Irish estuaries and tidal inlets, though relatively few survive in any recognisable form.

The structure, recorded in February 1997 by archaeologist Aidan O'Sullivan, runs roughly northeast to southwest and measures approximately eight metres in length. It sits around ten metres north of a related feature on the same stretch of foreshore. O'Sullivan's survey of intertidal archaeology along the Shannon documented a number of such features in the area, placing this weir within a broader pattern of post-medieval fishing activity on the estuary. The date range of "post-medieval" suggests use sometime after the sixteenth century, though the basic technology of driving posts into a tidal creek to trap fish is far older and was in continuous use across many centuries and cultures.