It is mandatory to replace the trimmer line if you run out of it or in case it gets unfastened or spoiled. Purchase a weed eater string compliant with your trimmer. Then follow this procedure to string a weed eater. Shut off and disconnect the power supply of the weed eater. Make sure it is not overheated. Remove any grass or weed remains to prevent clogging. Twist the trimmer head to uncover the remaining string on the spool. Be careful not to break off the spool piece attached to the weed eater. Take out the extra leftover string piece. Introduce the new string tip into the string hole. Start rotating the spool to wind up the string around it. Keep rotating until you get the required length of string around the spool. Leave about 6 inches of extended weed eater string outside the spool. Trim the string with the spring cutter provided with it. Close the head and make sure to lock it properly. You are now ready to go trimming. If the weed eater does not start, switch it off, then try reopening the trimmer head. Readjust the string on the spool if it is dislocated. This will probably start the weed eater machine.