Seed sowers or drills are now indispensable in commercial gardening, because they do the work so much better and more rapidly than is possible by hand sowing. The seeds are deposited before the soil has had time to dry out; the depth of covering is uniform and the soil is compacted after sowing; the rows are also straighter and the seeds can be dropped in hills, if this is desired. There are several standard makes of seed drills, all of them satisfactory when properly used. Figure 29 shows the drills used most extensively. A wheel hoe and a drill are sometimes combined in one implement, but the tool is not very popular with commercial growers.