Press the spool down GENTLY and rotate it until you feel it drop into place. (When in place, the spool will turn a few degrees left and right freely). Take care to keep the line from becoming trapped under the spool. Snap the hub cover back on, and turn the tool on.
How does the Stihl AutoCut head work?
The AutoCut mowing head has a line storage device and the line is fed while the machine is running. This is done by tapping the top of the mowing head on the ground. This opens the holding mechanism for the line and centrifugal force causes line to be fed out.