In another important respect the manorial system survived long after serfdom had begun to decline. This was the method of doing farm work. A universal and insistent tradition had fixed agricultural method on the medieval manor and tended to preserve it unaltered well into modern times. The tradition was that of the "three-field system" of agriculture. The land of the manor, which might vary in amount from a few hundred to five thousand acres, was not divided up into farms of irregular shape and size, as it would be now. The waste-land, which could be used only for pasture, and the woodland on the outskirts of the clearing, were treated as "commons," that is to say, each villager, as well as the lord of the manor, might freely gather fire-wood, or he might turn his swine loose to feed on the acorns in the forest and his cattle to graze over the entire pasture. The cultivable or arable land was divided into several--usually three--great grain fields. Ridges or "balks" of unplowed turf divided each field into long parallel strips, which were usually forty rods or a furlong (furrow-long) in length, and from one to four rods wide. Each peasant had exclusive right to one or more of these strips in each of the three great fields, making, say, thirty acres in all; [Footnote: In some localities it was usual to redistribute these strips every year. In that way the greater part of the manor was theoretically "common" land, and no peasant had a right of private ownership to any one strip.] the lord too had individual right to a number of strips in the great fields. [Sidenote: Disadvantages of Three-field System of Agriculture]