Turrets were built at equal distances between milecastles and there were two such buildings between each of the latter and were spaced at one every third of a Roman mile. These were primarily watch towers and were built of stone regardless of whether or not they were on the stone or turf wall. Their size would be approximately 20 feet square and recessed into the wall by roughly 6 feet. The height of a turret could easily be as high as 30 feet without any strain on the foundations and this is a perfectly reasonable height to assume. A doorway gave access to the turret from the south wall. To the side of the door would be a platform, added later, where possibly a timber stairway gave access to the upper floor or walkway of the Wall. This seems more likely than the other theory of a timber based ladder which has been a long held belief.
In the turf wall turrets there is no platform where they existed in the stone building but a dais is normally found which could have served as a base for a stair or, as has been suggested, a raised bench for a soldier to eat from or keep his blanket clean when folding simply because the floor would be filthy. The soldier in the turret, through popular belief, would sleep on the floor and therefore, for security, only a strong bolt would be needed to lock the door. It is popularly believed that the roof of the turret would be flat using stone flags to complete it. However, I and others, take the view a sloped roof would be used here. Evidence for the former is non-existent while only sparse remains of slates and a single fragment of a roof tile have been found so far. More evidence is needed to clarify how the roof of a turret would look although other theories include a thatched roof which means no evidence is likely to remain.
Evidence based on the designs depicted on the Rudge Cup and Amiens Skillet cannot be taken literally as they could quite easily just be an artistic representation of the Wall and turrets, given that these objects could be souvenirs made around the 2nd Century AD. Inside the turret would be a hearth used for cooking and, of course, this was on the ground floor. Normal finds such as quernstones, gaming counters and other domestic utilities have been excavated in turrets which does suggest soldiers living and sleeping here but it cannot be proven archaeologically given the nature of such things. Window glass has been found giving rise to possible glass based windows but, again, it cannot be proven and there is the possibility that simple shutters would be used.
Turrets would be numbered to match the numbering system of milecastles along the Wall. Between each milecastle two turrets would be built. These would be every one third of a Roman mile. So, as an example, turrets between milecastles 2 and 3 would be numbered 2a and 2b and between milecastles 3 and 4 would be numbered 3a and 3b and so on.