Unplug the cord if the weed eater is electric powered or ensure the motor is off if it is gas powered.
Turn the weed eater over to gain access to the bottom of the head and the bump knob.
Place the weed eater between your legs while you are in a standing position. Position the head so it is in front of you.
Hold the weed eater with one hand and grasp the bump knob with the other.
Press down on the bump knob while you turn it counterclockwise. The knob will disengage from the head, exposing the spool of nylon line.