A string trimmer is a power operated device for the trimming and cutting of grass and weeds. A rotating head that contains a spool of plastic cutting line is mounted at the end of a shaft. The other end of the shaft has a handle and a trigger for the operation of the trimmer. The string is fed from the spool automatically or by tapping the bottom of the trimmer on the ground. Some string trimmers are electrically powered, while some are powered by a small gasoline engine. No matter which type of trimmer you own, the string will wear down from coming into contact with concrete, fence posts, or any other obstruction. When all the string in the spool has been depleted, a new length of string will need to be refilled.
Turn the trimmer's main power switch off. Unplug your trimmer if it is an electric model or remove the battery if it is a cordless unit.
Remove the centre spool cover located at the base of the trimmer's shaft by pressing in on the release tabs and pulling the cover straight off of the spool. Now pull the spool straight off of the shaft.
Unwind any remaining line from the spool and discard it.
Unwind a small section of replacement line. Insert about one half inch of the new line into the hole in the centre of the trimmer's spool. Start wrapping line around the spool evenly and tightly. Check the spool for a directional arrow, and if it has one, wind the line in the direction the arrow is pointing.
Continue winding new line onto the spool until it is almost full. Do not overfill the spool. Cut the line with a utility knife. Store any remaining unused line for future refills. Place the refilled spool near the trimmer and feed the cut-off end of the line through the hole in the trimmer head. Push down on the spool until it snaps into place.
Pull on the line protruding from the hole in the trimmer head until all slack is taken up. Push the spool cover back on until it snaps into place.
Turn the trimmer on so that any excess line is cut to the correct length automatically before you begin trimming.
Make sure you use the correct diameter of line for your trimmer. Using the wrong line will cause your trimmer to malfunction and possibly damage itself.