Remove the truss rod cover, if so equipped, and apply a capo at the 1st fret. Press down the 6th string at the 14th fret with your right hand. With a feeler gauge, measure the distance between the top of the 5th fret and the bottom of the 6th string. There should be a small gap (.006"+/- .002"); remember this gap will be one-half the thickness of the 1st string (.012"). This will determine the "neck relief" necessary to prevent string "buzz" caused by the normal vibration pattern (string excursion) of the strings. Less than a .006" gap may cause a "buzz" or cause "fret out" if some high frets exist. On Guild guitars, use a 1/4" nut driver to turn the truss rod clockwise to straighten the neck or counter-clockwise to add some "relief". Note: Medium gauge strings (.013"-.056") have higher tension, with less "string excursion", needing more truss rod tension to counteract the stronger string pull. This results in more volume, sustain and more "wood" in the guitar's tone. Note: In either case, if you meet excessive resistance or need for adjustment, or you're not comfortable with this adjustment, take your guitar to your authorized Guild Service Center.