which a ceorl could become a thegn. Again these would have been subject to local variation, but one text refers to the possession of five hides of land (around 600 acres), a bell and a castle-gate, a seat and a special office in the king's hall. In the context of the control of boroughs, Frank Stenton notes that according to an 11th-century source, "a merchant who had carried out three voyages at his own charge [had also been] regarded as of thegnly status." Loss of status could also occur, as with penal slavery, which could be imposed not only on the perpetrator of a crime but on his wife and family. A further division in Anglo-Saxon society was between slave and free. Slavery was not as common as in other societies, but appears to have been present throughout the period. Both the freemen and slaves were hierarchically structured, with several classes of freemen and many types of slaves. These varied at different times and in different areas, but the most prominent ranks within free society were the king, the nobleman or thegn, and the ordinary freeman or ceorl. They were differentiated primarily by the value of their weregild or 'man price', which was not only the amount payable in compensation for homicide, but was also used as the basis for other legal formulations such as the value of the oath that they could swear in a court of law. Slaves had no weregild, as offences against them were taken to be offences against their owners, but the earliest laws set out a detailed scale of penalties depending both on the type of slave and the rank of owner. Some slaves may have been members of the native British population conquered by the Anglo-Saxons when they arrived from the continent; others may have been captured in wars between the early kingdoms, or have sold themselves for food in times of famine. However, slavery was not always permanent, and slaves who had gained their freedom would become part of an underclass of freedmen below the rank of ceorl. Culture Architecture Early Anglo-Saxon buildings in Britain were generally simple, not using masonry except in foundations but constructed mainly using timber with thatch roofing. Generally preferring not to settle within the old Roman cities, the Anglo-Saxons built small towns near their centres of agriculture, at fords in rivers, or near natural ports. In each