Lawn aeration is the secret weapon in making your lawn healthy. Aeration involves making holes in the lawn either by pushing a rod into it or by "coring", extracting a plug of soil. Lawn Dethatching is removing the thick thatch layers built up between the soil and grass. Thatch is the natural accumulation of living and dead matter. Manual power raking is usually the best method as it provides the least amount of stress to the existing sod root system.