The hide was an English unit of land measurement originally intended to represent the amount of land sufficient to support a household. It was traditionally taken to be 120 acres (49 hectares), but was in fact a measure of value and tax assessment, including obligations for food-rent (feorm), maintenance and repair of bridges and fortifications, manpower for the army (fyrd), and (eventually) the geld land tax. The hide's method of calculation is now obscure: different properties with the same hidage could vary greatly in extent even in the same county. Following the Norman Conquest of England, the hidage assessments were recorded in the Domesday Book of 1086, and there was a tendency for land producing £1 of income per year to be assessed at 1 hide. The Norman kings continued to use the unit for their tax assessments until the end of the 12th century.