Whether corded or battery-powered, electric string trimmers make maintaining your lawn a lot easier. String is wound on a spool in the cutting head of the trimmer. As the trimmer spins and cuts, the string will wear out and break off. New string is automatically fed when the cutting head is tapped on the ground. The string won't last forever, though, and will eventually need to be replaced. Re-stringing is a relatively easy procedure.
Removing the Spool and Preparing the String
Turn off and unplug the string trimmer.
Remove the spool retainer that holds the spool in place on the underside of the cutting head and set it aside.
Remove the spool from the spool head. You may notice a spring either on the spool on on the cutting head. Keep the spring in place.
Remove any old string from the spool.
Cut a length of new trimmer string 9 feet long. If the trimmer requires two strings, cut another of equal length.
Loading the Spool
Hold the spool facing down and insert the end of a string into the little anchor hole in the side of the spool. If the trimmer uses two strings, install the string in the upper area first.
Check the spool for an arrow that indicates the direction to wind the string. Wind the string around the spool until approximately 6 inches remain.
Press the string into one of the string retention slots in the upper spool flange.
Insert the second string, if the trimmer takes two strings, into the anchor hole in the lower area of the spool.
Wind this string around the lower area of the spool until approximately 6 inches remain and press the string into the other string retention slot in the upper spool flange.
Replacing the Spool
Insert the end of each string through a guide hole in the cutting head and pull through to around 5 inches.
Position the spool over the cutting head shaft and press the spool down onto the shaft.
When the spool is properly positioned, pull the strings sharply to release them from the retention slots.
Rotate the spool until it no longer turns.
Replace the spool retainer, turning accordingly to tighten it to the shaft.
Pull the strings once more to align the spool into cutting position.