Hitachi CG25EJ Owner's Manual page 10

When using a trimmer head (2) with two piece
type blade guard, attach the guard extension to
the blade guard. (Fig. 1-9)
NOTE!
If your unit has guard location label on drive
shaft tube, follow the indication.
Fig. 1-9
Fig. 1-9C
NOTE!
To remove the guard extension, refer to the
drawings. Wear gloves as the extension has a
sharp line limiter, then push the four square tabs
on the guard one by one in order. (Fig. 1-9C)
G
B
GB-9