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Remove your grass turf if you are leveling the entire yard. Mow any existing patches of lawn you plan to level. Find areas in your yard that you want to level. Use a line level to determine the highs and lows of your yard. Record areas that need raising or lowering on a piece of paper. Leave your string and stakes up while you're working.
If your yard is extremely bumpy and your grass is full of weeds, you may need to replace the lawn entirely. Dig up the existing turf with a shovel or kill it with a chemical herbicide or organic alternative to get rid of the grass quickly.  At least 2 days before digging or excavating, you should request utility locates. In the U.S., you can call the national Digline at 811. This is a free service. Some grass may have roots up to 1 foot (30 cm) deep that will need to be removed. If you are not leveling your whole yard, you do not need to remove your grass entirely. Mowing the area down will help you see the raised and lowered areas clearly as you work. It will also allow you to apply topsoil directly to the ground later on. If you notice uneven areas while mowing, mark them with a small sprinkler-marking flags. Look for uneven areas in your yard that could use leveling. Drive a stake into the 4 corners of the area that you choose. Tie string around the tops of the stakes to make the area you plan to level clear while you work.  If you are leveling your entire yard, plan to finish the project over a period of several days rather than an afternoon. Don't worry about precise measurements while marking off the yard area. The area does not need to be even or perfectly rectangular. Attach the line level to the string to measure the highs and lows of your area. As you string the level along the line, watch the bubble on the line level's cover. If it is in between the 2 lines, the ground is level. If it is shifted to the right or left of either lines, the ground is uneven. Take measurements every 4–8 feet (1.2–2.4 m) as you go around the perimeter of the area, marking which areas will need to be raised or lowered later on. If you notice a raised or lowered area as you level that you had not measured, use your line level to measure it before working on it. Refer to your notes any time that you can't remember which areas in your yard need to be leveled during the process. Making a to-scale drawing on graph paper can be very helpful as well. As you level your yard, you will need to continue taking precise measurements. Leave the stakes and strings up as you work. If the stakes tilt or fall over while you work, prop them back up in case you need to use your line level again later.