Replacing your grass trimmer's line is a quick and easy procedure that will keep your tool operating properly. Replacing the line is a slightly more involved process than simply dropping in a pre-wound replacement spool, but it comes with cost-saving benefits and allows you to install a line sized to meet your yard-trimming needs. A single bulk spool of line will last several changes.
Unplug the trimmer or remove the spark plug if the trimmer is gas powered to prevent accidental start up. Place the trimmer on a flat surface so that the trim head is facing upwards.
Remove the trim head cover. Either unscrew the cover or press in the side retaining clips depending on your brand and model. Some may be held in place by a bolt.
Separate the spool from the trim head, and remove any old or broken line.
Cut a piece of replacement line to length. Line varies in thickness, and certain trimmers may require you use a certain diameter line. This will be marked on the spool. Thicker line is good for cutting thicker grass, while thin line is good for areas with sparse coverage. Most trimmers will hold about 10 to 20 feet of line. It is always better to cut a longer piece and trim it down later.
Insert one end of the line into the retaining hole or slot.
Wind the line around the spool in the direction indicated by the arrow. Wind the line until the spool is 3/4 full, and leave a piece of line measuring about 6 inches extending from the spool. Trim the line to size if necessary.
Clip the loose end of the line into the retaining slot on the outer spool flange.
Thread the end of the line into the hole on the trim head, and insert the spool in place. Pull on the line emerging from the trim head until it comes free of the retaining clip.
Reinstall the spool cover.