Turret 12A (Heddon West) is located beside (and mainly beneath) the B6318 Military Road a short distance West North West of Heddon-on-the-Wall.[4] No surface traces are currently visible.[5]
The turret was located in 1928 as 548 yards (501 m) west of Milecastle 12. This location was confirmed by a partial excavation in 1930. It was found that the walls were reduced to ground level beyond the edge of the roadway, but had the same plan as Turret 12B. However, the platform (which occupied the South side of the interior of Turrets 12B and 13A), was too badly robbed for any trace to remain.[5] The mortared walls were recorded as 1.22 metres (4.0 ft) thick, with the doorway lying to the east.[2]
Location on Ordnance Survey 1:25 000 map: 54.998174°N 1.797620°W[4]