After a field had been plowed, harrows were used to break up clods or clumps of sod, prepare fields for planting, and maintain pastures. A disk harrow broke up clumps of sod, with rocks placed in rectangular trays above the disks for added weight. A spring tooth harrow broke up clods of soil and, with a wooden double tree and two single trees, was set up for two horses. A framed, lever harrow finished plowed fields prior to planting, and its operating levers controlled the depth at which it worked while the operator walked behind it and controlled the horses. A spike toothed, aerator disk loosened and oxygenated soil that had been compacted by livestock, and rocks in rectangular trays provided added weight.