This is a blade lock nut that is typically a component of string trimmers and edgers. The blade lock nut ensures the cutting blade is securely attached to the shaft of the trimmer. If the nut is corroded, broken, or has come loose, it will need to be replaced. The equipment should not be operated without this nut since other components could come loose and fall off.This is a simple part to replace and will require only a wrench or a socket set. This nut is located on the spindle, so a visual inspection can be done to ensure it is damaged or broken. Remove it and thread the new blade lock nut to the same location. If the nut is stripped, a bolt remover can be used to get it off of the lawn equipment.This blade lock nut is sold as an individual part. It is an authentic OEM replacement part that is sourced directly from the manufacturer. The part is made to fit a variety of edgers and string trimmers manufactured by Craftsman, Cub Cadet, MTD, Ryobi, and Yard Machines.