Parker Fly Handbook page 15

Adjusting the Truss Rod
The truss rod is easily accessible, via the hole located on the bottom edge of
the headstock. To adjust the rod, use the Torx wrench supplied with your
guitar. Turn it clockwise to tighten the rod, and counterclockwise to loosen it.
Be aware that the rod adjustment is very sensitive, one-sixth turn yields a
lot of movement. For example, changing from .009" to .010" string
gauge will require as little as a 1/4 turn clockwise of the truss rod.
If you're unfamiliar with adjusting a
truss rod, we strongly suggest that you
take your instrument to your favorite
guitar technician. Misadjusting the truss
rod can cause irreparable damage to
your instrument.