Behind the scarp revetments there are three long galleries incorporating casemated rooms for both musketry and carronades, all for the defence of the ditch. These are constructed mainly in brick laid to English bond, usually with axial semi-circular vaults of stretchers, invariably whitewashed. The north Musketry gallery consists of 26 casemates and a single horizontal musket loop flanking the east face of the caponier. (location accurate to the nearest 1m based on available information)