Turning towards the bass side straightens the neck on a Hamer, Gibson, any other guitar with a truss rod. Turning towards the treble side allows the strings to bow the neck. On a double action truss rod, turning towards the treble side will eventually add bow, regardless of string tension. With a Fender, the adjustment is on the body end, so the above is reversed. Hamer uses single action truss rods, as does Fender.