Clapper bridges are among the most elemental forms of river crossing, built by laying flat stone slabs directly onto low piers with no mortar, no arch, and no pretence of engineering sophistication. What you get instead is something closer to a stone path that happens to pass over water, and this example on the Douglas is a good one: nineteen metres long, made up of eleven slabs, each roughly 1.9 metres in length and just twelve centimetres thick, resting on eight rough masonry piers that stand about ninety centimetres above the riverbed.

The proportions are precise enough to picture clearly. The slabs are narrow, around fifty-five centimetres wide, meaning two people could not easily pass one another mid-crossing without a certain amount of negotiation. The piers are described as rough masonry, which is to say they are functional rather than dressed, stones stacked and fitted without any particular finish. Somewhere along the southeast end of the bridge, a number of slabs have slipped from their piers and fallen into the river, leaving that section incomplete. It is a small but telling detail: without mortar or any fixing mechanism, these structures rely entirely on weight and careful placement to hold together, and occasionally they do not.