Your lawn mower is meant to cut grass simply, evenly and with minimal effort. With proper maintenance, your mower will continue to cut well for years. A neglected maintenance measure is the removal and sharpening of your mower blades. Taking off your blade and removing caked-on grass from the bottom of the mower will make your mower cut more efficiently, and sharpening the blade will prevent you from having to replace it prematurely.
Put on a pair of heavy work gloves and safety glasses to prevent loose debris from getting in your eyes and to keep you from skinning your knuckles on the underside of your mower.
Remove the oil and gasoline from your mower to prevent it from draining into the carburetor during the repair.
Turn the mower over so that the oil crankcase and gasoline tank are underneath the carburetor, which will prevent any liquid still left from draining into the carburetor.
Place a scrap piece of wood at the bottom of the mower, and force the blade into it to prevent the blade from moving while loosening it, which will prevent injury.
Adjust your wrench around the nut holding the blade and loosen the bolt, which may be difficult to achieve as it will be quite tight. If you cannot get the bolt loose, use the rubber mallet against the wrench to get the bolt moving.
Remove the bolt from the mower, and take the blade off the nut. Clean the underneath of the mower with a putty knife to remove grass.