My elderly neighbor gave me his weedeater and we can't seem to get the trimmer line housing apart to replace the line. Any help appreciated model# SG-11

Most weedeater use a bump and run head. There should be a black knob-like fitting in the head that is designed to be bumped on a hard surface. This feeds out more line. There is normally a large nut above the head, clamp that in a vise or with a wrench. Inspect the shaft or head for a small round hole. You can insert a nail or other hard round shaft into the hole, rotate the knob while pushing in with the nail. The nail should fall into place and lock the shaft from rotating. Then just unscrew the knob, lefty-loosey.