The great wall of Hadrian comes to an end at Bowness-on-Solway at a large fort on high ground commanding the narrowest part of the Solway Firth. In the first phase of construction a curtain of laid turf was planned and executed from the River Irthing to Bowness, and there is a hint, from the fortlets and towers of the Cumberland coast, that provision had been made for the turf curtain to continue beyond Bowness. The change of plan that brought the garrisons of the Stanegate frontier forts forward to new forts on the Wall also moved the garrison in the fort at Kirkbride to a new fort at Bowness and added the fort at Beckfoot to the coastal system at the position of Tower 14B. The units in the coastal watch and patrol system comprised stone-built towers and turf and timber fortlets, the fortlets being quite accurately set out close to the shore-line at intervals of one Roman mile, each mile being divided into three parts by two towers.