The most striking feature about the manors is that each was almost completely self-supporting. Each manor provided corn, meat, eggs, milk, cheese, poultry, &c., for its own inhabitants. Fuel, and perhaps game and rabbits, came from the waste. The furniture was of rude wood, and the clothes would be sheep-skin and coarse cloth spun and woven from the wool grown on the sheep that were fed on the manor lands. The ordinary serf would very rarely either receive or spend coin of the realm. Salt he would buy and the metal pots and pans used for cooking, and, as Ashley suggests, tar.[26] But the greater amount of the goods required for himself and his family would be produced under what the economists call "natural economy," _i.e._ they were made by the people who intended to use them, directly, without the intervention of money or any mechanism of exchange. Together with this self-sufficiency would go a considerable amount of co-operation. Economists are not yet agreed as to the precise extent to which co-operation was used in the manorial village. But we know that tenants frequently lent their oxen to one another to make up the necessary team; that in some of the Durham manors there was a communal smith, who received payment in the possession of a strip of land; and that the tenants owned a common oven. It was customary, too, for one shepherd or swineherd to guard the sheep or the pigs of the whole community. The village mill, when first established, was also a common boon to the whole body of serfs, but later on the obligation to grind their corn at the lord's mill and to pay the dues came to be regarded as an onerous burden. A curious and important person on the mediæval estate was the bee-keeper. Particulars are given of his duties and rewards in one Durham manor by the Boldon Book.[27] He does no regular weekly work, the care of the bees apparently taking the place of this, but he must take part with the other serfs in the boon-works necessary at harvest and other times of pressure. As honey was almost the only source of sweetness in early mediæval cooking, it can be understood why the bee-keeper ranked only a little below the shepherd. The Boldon Book, unfortunately, since its aim is to define the relations between the villeins and their lord, does not tell us whether he superintended the bees belonging to his fellow tenants. On the analogy of the shepherd and swineherd, we should assume that he did.