Turn off the mower and disconnect the power cord, if your Weed Eater is electric. Allow 15 minutes for the engine to cool down.
Turn the Weed Eater on end so the trimmer head is facing upward. Place the adjustable wrench tightly around the dust cup bolt above the head.
Turn the head counterclockwise by hand to remove it from the Weed Eater. Set the old head to one side.
Place the replacement trimmer head over the shaft and turn clockwise. Stop when the trimmer head is hand tight -- do not tighten the head with a tool. The replacement head has now been successfully installed.