These milefortlets and intervening stone watchtowers extended from the western end of Hadrian's Wall, along the Cumbrian coast and were linked by a wooden palisade.

Milefortlet 4 is situated at the seaward edge of a low ridge, just north of the hamlet of Cardurnock in the civil parish of Bowness.

[1] There is nothing to see from the ground but a geophysical survey of the site was undertaken in 1994 and the precise position of the milefortlet was located.

[1] Each milefortlet had two associated towers, similar in construction to the turrets built along Hadrian's Wall.

[2][3] The position of Tower 4A is uncertain, although it thought to lie on the crest of a ridge with good views seaward.