Plan is aligned with North at the top of the image.
Birrens Roman Fort was occupied for long(many years) at a time,and as such is a good example of what a huge undertaking Hadrian's Wall was,even in its day.The ramparts of this fort,were constructed using turfs.The Roman military manual,copies of which still exist today,was very specific as to what constituted a turf.It was 18 inches square by 6 inches deep.It was using such"building bricks",which had always previously been used,on the German"limes",for example,that Hadrian's Wall was initially constructed with.Just over half the length of the Wall had been built using this method,when it was decided to use stone,instead.