The distance from the strings to the fingerboard is also determined by the position of the neck. There are two elements of neck position: neck angle and the curvature of the neck, sometimes called relief. Neck angle is seldom something that the player can change, but knowing about it will help you determine what needs to be done to improve the playability of a guitar. Most bolt-on neck electric guitars and most acoustic guitars are built with what is called a zero neck angle. This means that the plane of the neck and the plane of the body of the guitar are the same. On a few acoustic guitars and some set-neck (glue-in neck) electrics (the Gibson Les Paul, for example), the neck is tipped back slightly (usually 3-4 degrees) from the plane of the body. You can most easily detect this tipped back neck angle by laying your guitar flat on its back on a table or the floor. With the body resting flat, the neck will tip slightly toward the tabletop, sometimes enough to have the headstock rest on the tabletop. On a zero neck angle guitar, the neck should be more or less parallel to the tabletop when the guitar is resting on its back. There is no right or wrong with respect to guitar construction, but a tipped back neck will require a taller bridge in order to play properly.

Sometimes, as a consequence of age or a poorly cut neck joint, a guitar neck will be tipped forward. When the guitar is resting on its back, if the neck points away from the table, the neck is improperly tipped forward. Another way to detect this condition is when a guitar has a rather high action but a very low bridge height. On expensive acoustic guitars, the owner may want to pay a qualified professional repairperson to reset the neck. This is a major surgical procedure that involves removing the neck from the guitar, reshaping the joint, and re-attaching the neck to the guitar. This job can cost from $300 to $500, and should never be done by someone who is not qualified and experienced. That a neck angle changes over time in response to the pull of the strings (about 160 lbs. for a set of light gauge acoustic strings) is normal in acoustic guitars. The more a guitar is played, the more slowly this change takes place.

On inexpensive acoustic guitars, there is little that can be done that is economically sensible to repair a bad neck angle. These guitars are best relegated to being put in an open tuning and played with a slide. A bolt-on neck guitar with a bad neck angle can sometimes be shimmed at the front of the neck pocket to make it playable again. Sometimes these guitars, too, are best made into slide guitars. A good repairperson can help you figure that out.

Neck relief, or how much a neck is bowed, is different from neck angle. Relief is controlled by the truss rod. Neck relief can be examined by sighting down the neck when the guitar is tuned to pitch, but is best determined using a straightedge laid on the frets when the guitar is tuned up. On most guitars, relief only is present between the first and twelfth frets so you can also fret the guitar at the first and twelfth frets simultaneously, and see how much the neck is curved relative to the string.

The more relief (or forward bow) that is in a neck, the farther the strings will be away from the fingerboard. Which is to say that the straighter the neck (or even the more back-bowed a neck), the closer the strings will be to the fingerboard. This having been said, the truss rod should almost never be used to adjust the action on a guitar. The proper amount of relief in a neck (from dead flat to bowed forward) is a function of how a particular player plays and what strings he or she uses. The harder a person plays, and the heavier strings they use, the more relief they will need in the neck to keep the strings from buzzing on the frets, especially in the middle region (frets 3 to 8) of the neck. This is because with a heavy attack and heavy strings, the excursion (movement) of the strings is greater, thus necessitating more room above the fingerboard to allow them to move. The middle region of the neck is where the wave motion of the strings causes them to move the most. Conversely, a person who plays with a very light right hand attack and uses very light strings, may be able to get away with a neck that is dead flat. There is no right or wrong amount of relief (within reason), except as it pertains to a particular player and their individual playing style, however, a back bowed neck is never desirable and will almost always cause fret buzz.

The nut, or top nut, is often the last place most people look for when they are looking to improve the playability of a guitar, but it, too, is very important, especially to first position playing. The nut is the small, grooved plastic or bone piece at the top of the fingerboard that supports the strings as they pass from the tuning pegs to the playing surface of the neck. It controls the height of the strings off the first fret and if too high, can render first position playing murderously difficult, and out of tune.

To determine if nut height is properly adjusted, place the guitar across your knee and fret all the strings by barring across them in front of the third fret with the first finger of your right hand. Look carefully at the space between the top of the first fret and the bottom of the strings. You may need to press the strings down with your left hand (one at a time) to determine how much, if any, space is between them. A properly adjusted nut will hold the strings just a hair’s breadth (literally) above the first fret when examined in this fashion. It is often desirable to have the bass strings higher than the treble strings, with a gradual progression (higher to lower) from sixth to first string. A nut that is too low will cause the open strings to clatter on the first fret; a nut that is too high will make the guitar difficult to play, especially in lower positions. Sometimes a nut will have some strings that are too high and some that are too low. A properly adjusted nut should also let the strings pass through the grooves freely, while holding the string in place from side to side, with the nut slot canted backward toward the tuning pegs. A little graphite (pencil lead) rubbed in the string slots will go a long way to helping out string movement, which will help a guitar stay in tune. Lubricating the string grooves in this way every time you change strings is a good idea.

So, as we can see, playability of a guitar is not determined by just one factor, but a combination of factors that define the interrelationship of the parts of a guitar, specifically, the distance from the strings to the fingerboard. This is what determines how much effort it takes to push the strings down to the frets. Playability is also influenced by string tension, which is controlled by tuning and the gauge of strings, i.e., the heavier the string and the higher the pitch, the more tension, which results in more effort to push the string to the fret.