this gear train lobed wheel must be insert in the opening in the floor of the microwave ovenm,for the purpose ,open the door and guide the washer over the shaft of the gear train lobed wheel. Now stick the gear train lobed wheel into the opening in the floor.Put the roller ring into the depression inside the appliance.place the turntable on the roller ring in such a way that the notches in the turntable click into place in the gear train lobed wheel