A weed trimmer can help you maintain hard-to-reach areas of your landscape that your lawn mower can't, such as against a fence. All weed trimmer models have a spool of string at the end. This string spins quickly and is the actual mechanism that cuts back vegetation. Over time, you will have to replace the string as it wears away. The same general principles for replacing the string can be applied to all weed trimmers, regardless of the specific manufacturer or model.
Turn off the weed trimmer. Set it on its side with the weed trimmer's head--the part with the string--facing you.
Locate the string spool piece, found in the middle of the weed trimmer's head. Take off the plastic cap that covers the spool. You may be able to pop it off with your fingers. Depending on your weed trimmer model, you may have to pry it open or unscrew it with a screwdriver.
Wrap new string around the spool. Feed the ends of the string through the one or two holes found on the side of the spool piece. Allow approximately 1 inch of string to stick through the holes.
Replace the plastic cap.