Most people do not realize the full significance of the little metal bars that span the width of most guitar necks. Some assume that they are simply for decorative purposes. Others believe them to indicate the locations at which a guitarist must place his or her fingers. This second notion is partially correct, but it is far from the full truth of the matter. These bars, which are called frets, divide the neck of a guitar into fixed segments at intervals. These intervals are related to a musical framework, one that allows the instrument to be played effectively and correctly. On a standard Western-style guitar, each fret represents one semitone, twelve of which make up an octave.

The position of a fret, as mentioned, indicates where a guitarist must press down on a string in order to produce a desired note. The logistics of this technique are as follows: when a string is depressed against a fret, the vibrating length of that string is reduced. The length of the vibrating string is what determines the note created. Accordingly, frets on a guitar make it much easier to create not only the correct intonation, but the correct chords as well.

In its typical form, a fret simply spans the width of the guitar's fingerboard at a given point. However, there are several variations to this standard format. The slanted fret, for example, is slanted across the fingerboard instead of running perpendicular to the instrument's neck. Some argue that slanted frets are more ergonomically correct, but this has not managed to inspire a large following. Only a few modern guitar manufacturers offer instruments with slanted frets. However, the use of such frets is actually quite old, dating back to at least the 16th century when it was used on the orpharion, a kind of lute.

Another variant on the standard fret is the scalloped fingerboard. This attribute is created when the luthier (guitar maker) scoops out the wood of the fingerboard between each fret, creating a shallow U-shape. On scalloped fingerboards, the guitarist's fingers only ever come into contact with the strings, never the fingerboard. This allows the artists to perform very rapid music. Guitars with scalloped fingerboards tend to be very expensive because of the amount of time and effort it takes to create such fingerboards. These guitars are usually favored only by shred guitarists, or artists who focus on fast passages. Scalloped fingerboards can also be seen on some more ancient instruments, such as the sitar.

Finally, retractable frets are yet another option to standard frets. These frets, as the name suggests, are designed to withdraw into the fingerboard as needed. The result is a smooth fingerboard surface like that of a fretless instrument. The advantage to this design is that it allows for greater versatility: in theory, the guitarists may switch between a fretted and fretless instrument as desired. However, the reality is that the mechanism controlling the frets' retraction is fairly cumbersome. It resides at the base of the guitar's neck, occupying a significant amount of space. The result is that guitars with retractable frets often have reduced musical ranges when used as fretted instruments.