added by archaeologs [or mile castle]. A small Roman fort set at intervals of one Roman mile along a major well-defended frontier (limes). On Hadrian s Wall examples show a small rectangular plan. A gateway in the wall, with watchtower over, permitted access into an area of offices and barrack quarters for up to about 30 men, and a second gateway (in line) then gave access to Roman territory.
The Macmillan dictionary of archaeology, Ruth D. Whitehouse, 1983