In early Anglo-Saxon England the hide was used as the basis for assessing the amount of food rent due from an area (known as "feorm"). Initially the size of the hide varied according to value and resources of the land itself. Over time the hide became the unit on which all public obligation was assessed; as well as food rent, the manning and maintenance of the walls of a burh and the amount of geld payable was based on the hide. Tenants had a threefold obligation related to their landholding; the so-called ‘common burdens' of military service, fortress work, and bridge repair. Later the hide was given a set acreage and in the Domesday book the most common size in use was . However some areas such as Dorset and Wiltshire used units based on to .