A lawn will need regular attention if it is to be an attractive feature in the garden. It may need repairing for a variety of reasons including wear and tear, mole damage, drought, or if frost lifts the turf. If bumps or hollows appear, follow these steps to keep your lawn level.
Using a half moon cutter, slice a cross shape right through the center of the bump or hollow and beyond its edges, making the cut as even as possible.
Use a turfing iron or a spade, and cut while making a slicing motion. The cut should be about 1-1/2 to 2 inches (4 to 5 cm) deep, and the spade should be kept as flat as possible to keep the turf at an even thickness.
Be careful not to break them. If the soil is dry, lightly water the grass beforehand. If you are only leveling a bump, dig out the soil until it is level with the surrounding area, and proceed to step six.
Fork over the soil to a depth of 2 inches (5 cm) to break up any compaction or large clods. Remove any large stones. After digging, tread it down lightly, otherwise it will sink again after repairing.
Fill each hollow until it is level with the surrounding soil. Rake it over to break the soil down to a fine tilth, and then add more if necessary. Add a pre-seeder fertilizer to the soil.
Firm each one down by tamping it with the back of a rake. Start at the edges of the square and work your way into the center. Do a final check to ensure that the ground is now level.
This will prevent the edges of the turf from drying out. Lawn seed can be sprinkled into the gaps to fill them. The lawn should then be watered to help it establish.
Original article and pictures take http://www.hgtv.com/design/outdoor-design/landscaping-and-hardscaping/how-to-create-a-level-lawn site