A grass trimmer is a portable lawn device with a rotating head on a pole that is used to edge grass and remove weeds in hard-to-reach places. The device uses monofilament line instead of blades to cut vegetation. Grass trimmers with monofilament line are designed for light cutting work. As the monofilament line wears, you can pull new line from the housing. Once the line in the housing is used up, replace it with new line. Threading a grass trimmer is not difficult.
Unplug an electric grass trimmer or disconnect the spark plug in a gasoline-powered trimmer before working on your string trimmer.
Grasp the trimmer firmly in one hand. Place your other hand over the trimmer hub, and twist it in the direction opposite of how the trimmer rotates it to unscrew the hub.
Pull the hub upward as soon as it unscrews from the trimmer head. Pull the spool off of the hub by grasping the hub in one hand and the spool in the other. Gently pull your hands apart.
Wipe the hub and spool clean of dust, dirt and grass residue with a clean cloth. Place the hub and spool on a flat surface for re-threading.
Cut a section of monofilament line that measures between 15 and 28 feet long. Fold the line double.
Place the center of the monofilament line in the spool's anchoring notch and wind the doubled line around the spool in the direction that the arrows printed on the side of the spool indicate.
Slip each end of the line through the exit holes in the hub when you finish winding your line around the spool. Pull enough line through the exit holes to trim grass with. Press the spool onto the hub until it snaps in place.
Reattach the hub to the string trimmer by aligning the hub with the head and screwing the hub back onto the trimmer.