The A837 crosses Cassley Bridge over the River Cassley just above its confluence with the River Oykel at Rosehall. It is a single track, twin arch stone bridge with unequal arches and triangular cutwaters to the central pier which stands in the middle of the river channel. It is tentatively dated as 1823, due to its similarities with the Shin Bridge nearby, which was built at that time. Unlike many of the old bridges in the local area, it is still in use, despite the slightly humped profile of the roadway making it difficult to see approaching traffic. The bridge is similar in design to the numerous bridges built across the Highlands by Thomas Telford. However, in this case, it was his former apprentice, Joseph Mitchell who was responsible for the structure in his capacity as surveyor for the county of Sutherland. The structure therefore features battered abutments and the parapets also curve down at their ends. Before they do so, however, they flare out to accommodate the wider approaches, with the roadway narrowing to single track to cross the bridge.