A fingerboard is the part of a string instrument on which the strings are stopped in order too change their pitch. The strings are tightened between the bridge and the nut (at the end of the neck), and pass over the fingerboard. A string is stopped by pressing the string with the finger to the fingerboard. Stopping a string at each point on its length changes its pitch accordingly.
The fingerboard is part of the design of most string instruments. Its shape and dimensions differ widely, according to the instrument. For bowed instruments, the fingerboard would be arched, in order to allow clearance for the bow when bowing each specific string. On plucked instruments, there is no need for clearance, and thus the fingerboard can be flat, which makes it simpler to construct.
The fingerboard is usually made of a single strip of wood attached to the neck of the instrument. In rare cases the fingerboard and neck are constructed together from the same piece of wood. The wood used for the fingerboard is generally hardwood. The fingerboard on modern violins, violas, cellos and contrabasses is made of ebony.
On instruments of the violin family the fingerboard extends beyond the neck and over the top plate in order to accomodate fingering of higher pitches. One of the reasons the fingerboard was designed as a seperate part from the neck, is that it can be replaced. The fingerboard (by being from a harder wood) adds strength to the neck, and (by being replaceable) allows the luthier to change the angle of the fingerboard to the body, and thus change the string action. Fingerboards of modern bowed instruments must be dressed, or "trued" usually about once a year. The constant playing actually creates deformities on the fingerboard surface, a slowly growing unevenness which eventually leads to buzzing of the strings when pressed at certain places. The process of dressing a fingerboard involves carefully sanding the fingerboard to create a smooth surface. eventually the fingerboard becomes too thin and needs to be replaced.
Cello and contrabass fingerboards are sometimes beveled. This means that the surface of the fingerboard under the lowest string is made flat instead of arched. This gives the string a few more millimeters of vibration clearance, and thus allows the player to bow the lowest string more vigorously, and produce a stronger bass sound.
Some fingerboards are fretted, for example on guitar and viol. The frets are a very easy solution for the problem of intonation on string instruments (although they actually introduce some minor intonation problems). Frets greatly facilitate the playing of chords, and also change the sound of the instrument considerably. On guitars the frets are strips of metal that are set in the wood of the fingerboard and can't be adjusted. On a viol (viola da gamba), for example, the frets are made of a gut thread (a piece of gut string), tied around the neck and fingerboard. These frets can be moved slightly up or down the neck in order to adjust the intonation.