[Sidenote: The geographical unit for food rents.] The structure of tribal society in Wales is one thing. The practical working of its rules is another. Until we can to some extent realise its methods and see how its results could be worked out in everyday life, it must remain to some extent vague and mysterious. The nearer we get to its core, the greater its value as an instrument in further research. We cannot, therefore, afford to disregard any hints that the Codes and surveys may give us, attention to which would help us to realise its methods or ways of working. [Sidenote: Districts called _villatæ_.] The Denbigh Extent, as already said, enables us to realise that, on the English conquest, the lordship of Denbigh was divided into grazing districts which had become the units of tribal food-rents, and which were adopted for purposes of future taxation. These districts were called by the scribes _villatæ_, and were occupied by gwelys of tribesmen and sometimes also by gwelys of non-tribesmen. Their homesteads or huts were occupied in severalty. Their grazing rights were undivided common rights, and within each gwely the rights of families and individuals were also undivided common rights. Further, the Denbigh Extent shows how easy it was to shift the whole body of tribesmen of this or that gwely, with its herds, from one district to another, according to convenience or the needs of population, without disturbing the complex rights within the gwely. The families and individuals carried their rights, _inter se_, with them wherever they and their herds might go, and were liable to pay the dues required from whatever villata for the time being might be occupied by them. Even the homesteads of the tribesmen seem to have been temporary, in the light of the description given by Giraldus Cambrensis. They could carry their hearth-stones with them wherever they went, so that the result seems to be that the groups of kindreds could always have been easily shifted about, as they were in fact after the English conquest, from one district or ‘villata’ to another. The geographical divisions thus became the permanent fiscal units in tribal arrangements. Both in the surveys and in the Codes we find the villata or district, and not the family group, the fixed unit for tribal food-rents to the chieftain, and for taxation after the English conquest. [Sidenote: The ‘tref’ or ‘maenol’ paying the ‘tunc pound.’] The surveys so far agree with the Codes. The _villata_ of the surveys was the taxable unit, and in some cases still paid the tunc pound (or 20_s._) in lieu of the chieftain’s food-rents. In other cases escheats and other causes had varied the amount. In the Codes of South Wales the unit for the tunc pound was the _tref_, and in the Venedotian Code of North Wales the _maenol_ of four trefs.