There seems to be a lot of mystery concerning how a neck should be setup using a truss rod or by shimming. The illustration shows the three typical setups that most of us will encounter with our necks. A. This is how the perfect setup would look. The neck itself is straight and the strings are set at an even distance from the frets along the entire length of the neck. B. This is a condition that is corrected using the truss rod. Note that the neck isn't straight and the strings are further from the frets near the middle but closer at both ends of the neck. You want to adjust in small increments until you get your neck looking like example A. The reverse of this condition is where the neck bows backwards and this too is corrected with the truss rod. Don't confuse a setup like this for the one described in example C. C. This is condition is only corrected by shimming the neck. Notice that the neck is straight but the strings gradually move away from the frets as they go towards the nut. Shimming alters the angle of the neck in relation to the body. You should never confuse this condition with the one shown in example B. Shimming is done by placing a thin spacer under the heel of the neck between the neck bolts and the bridge. This acts like a fulcrum and pitches the neck back to level the strings. I hope this helps with some of the confusion concerning the different ways necks need adjusting. If you aren't VERY confident in your knowledge of how to correct these conditions, don't attempt it! Damage can occur that will cost you more than if you were to take your instrument to a qualified technician.