You'll quickly come to rely on this simple tool. It's made from a four-inch-wide, four-foot-long board: Leave one of the long edges flat, or create a beveled edge by shaving it at a 45-degree angle with a table saw; you can also have a lumberyard cut it for you. Along the other long edge, cut alternating deep and shallow notches at 6-inch intervals. When planting seeds or setting out young plants, press the flat edge into the earth to make a furrow. Then lay the board on its side, and use the notches to help you space the seeds and seedlings evenly. For example, most lettuce seeds should be spaced 6 inches apart, so you can sow them at each notch. Tomatoes need 1 1/2 to 2 feet between plants, so put them in every three or four notches.