The raised structure to right of centre,in shot,was the double width gate in the north wall of the fort,through which movement of "cross wall traffic" was monitored.Sounds great,doesn't it?Official jargon.In reality,the gate opens to the north,atop a 50ft.high cliff,with only a narrow berm along the front of the fort.Traffic through here could only have been on horse back,or by foot.That is why,the Knag Burn Gate was built,100 yards to the east,at the foot of the cliff,to allow easy (no road,just rough trackways)passage through the wall.