Abstract: The present invention relates to a device designed to be detachably attached to the undercarriage of a lawn mower through the use of hooks engageable with the blades of the lawn mower. The device includes an annulus having a plurality of holes therethrough with a coupling designed to be connectable to a water supply hose. Additionally, a pair of diametrically opposed sharpening stones are rotatably mounted on the device and are automatically rotated through the provision of paddlewheels, each of which is rotated through the provision of water sprayed thereon as supply from two supply conduits. When the hose connection is connected to a hose supplying water to the device and the water begins to flow, water sprays out the openings in the annulus to clean the undercarriage of the lawn mower while water spraying out the supply conduits impinges on the paddlewheels causing the grinding stones to rotate to thereby sharpen the lawn mower blades.