Abstract: A method of making a cleaning device and a cleaning device for removing residue from the underside of a lawn mower including a lateral extension having a mower alignment guide with the extension sufficient high so an operator can operate the controls from the seat of a riding lawn mower, with the lawn mower cleaning device including reinforced members that carry an elongated wash arm having stakes thereon that can be driven into the ground to secure the wash arm in position for driving over with a riding lawn mower, with the wash arm having a minimum of sufficiently small openings so that the area of the openings is smaller in relation to the size of the plenum so the wash arm functions as a plenum chamber to thereby generate high pressure jets of water for cleaning the underside of the lawn mower.