information:classification, information:extraction
Neck

A guitar's frets, fretboard, tuners, headstock, and truss rod, all attached to a long wooden extension, collectively constitute its neck. The wood used to make the fretboard usually differs from the wood in the rest of the neck. The bending stress on the neck is considerable, particularly when heavier gauge strings are used (see Tuning), and the ability of the neck to resist bending (see Truss rod) is important to the guitar's ability to hold a constant pitch during tuning or when strings are fretted. The rigidity of the neck with respect to the body of the guitar is one determinant of a good instrument versus a poor-quality one.

The cross-section of the neck can also vary, from a gentle "C" curve to a more pronounced "V" curve. There are many different types of neck profiles available, giving the guitarist many options. Some aspects to consider in a guitar neck may be the overall width of the fretboard, scale (distance between the frets), the neck wood, the type of neck construction (for example, the neck may be glued in or bolted on), and the shape (profile) of the back of the neck. Other types of material used to make guitar necks are graphite (Steinberger guitars), aluminum (Kramer Guitars, Travis Bean and Veleno guitars), or carbon fiber (Modulus Guitars and ThreeGuitars). Double neck electric guitars have two necks, allowing the musician to quickly switch between guitar sounds.

The neck joint or heel is the point at which the neck is either bolted or glued to the body of the guitar. Almost all acoustic steel-string guitars, with the primary exception of Taylors, have glued (otherwise known as set) necks, while electric guitars are constructed using both types. Most classical guitars have a neck and headblock carved from one piece of wood, known as a "Spanish heel". Commonly used set neck joints include mortise and tenon joints (such as those used by C. F. Martin & Co.), dovetail joints (also used by C. F. Martin on the D-28 and similar models) and Spanish heel neck joints, which are named after the shoe they resemble and commonly found in classical guitars. All three types offer stability.

Bolt-on necks, though they are historically associated with cheaper instruments, do offer greater flexibility in the guitar's set-up, and allow easier access for neck joint maintenance and repairs. Another type of neck, only available for solid-body electric guitars, is the neck-through-body construction. These are designed so that everything from the machine heads down to the bridge is located on the same piece of wood. The sides (also known as wings) of the guitar are then glued to this central piece. Some luthiers prefer this method of construction as they claim it allows better sustain of each note. Some instruments may not have a neck joint at all, having the neck and sides built as one piece and the body built around it.

The fingerboard, also called the fretboard, is a piece of wood embedded with metal frets that comprises the top of the neck. It is flat on classical guitars and slightly curved crosswise on acoustic and electric guitars. The curvature of the fretboard is measured by the fretboard radius, which is the radius of a hypothetical circle of which the fretboard's surface constitutes a segment. The smaller the fretboard radius, the more noticeably curved the fretboard is. Most modern guitars feature a 12" neck radius, while older guitars from the 1960s and 1970s usually feature a 6-8" neck radius. Pinching a string against a fret on the fretboard effectively shortens the vibrating length of the string, producing a higher pitch.

Fretboards are most commonly made of rosewood, ebony, maple, and sometimes manufactured using composite materials such as HPL or resin. See the section "Neck" below for the importance of the length of the fretboard in connection to other dimensions of the guitar. The fingerboard plays an essential role in the treble tone for acoustic guitars. The quality of vibration of the fingerboard is the principal characteristic for generating the best treble tone. For that reason, ebony wood is better, but because of high use, ebony has become rare and extremely expensive. Most guitar manufacturers have adopted rosewood instead of ebony.