A fingerboard may be fretted, having raised strips of hard material perpendicular to the strings, which the player presses the strings against to stop the strings. On modern guitars, frets are typically made of metal. Frets let the player stop the string consistently in the same place, which enables the musician to play notes with the correct intonation. As well, frets do not dampen string vibrations as much as fingers alone on an unfretted fingerboard. Frets may be fixed, as on a guitar or mandolin, or movable, as on a lute. Fingerboards may also be unfretted, as they usually are on bowed instruments, where damping by the finger is of little consequence because of the sustained stimulation of the strings by the bow. Unfretted fingerboards allow a musician more control over subtle changes in pitch than fretted boards, but are generally considered harder to master. Fingerboards may also be, though uncommon, a hybrid of these two. Such a construction is seen on the sitar, where arched frets attach at the edges of a smooth fingerboard; unfrettable strings run inside the frets, while frettable ones run outside. The fret arches are sufficiently high that the exterior strings can be fretted without making the finger making contact with the interior strings, and Frets may be marked by inlays to make navigating the fingerboard easier.
On six-string guitars and bass guitars, markers are typically single smallish dots on the fingerboard and on its side that indicate the 3rd, 5th, 7th and 9th frets—and the octaves of those positions higher up the neck. A double dot or some other variation marks the 12th fret and 24th frets. Variations on the standard dot shape can make a guitar more distinctive. Position markers are sometimes made luminescent (through using paint, or illuminated with light emitting diodes) to make them more visible on stage. Position markers are also sometimes repeated on the edge of the fingerboard for easy viewing.
Over time, strings wear frets down, which can cause buzzing and deaden the sound. Fixing this occasionally requires replacing the frets—but more often they just need "dressing". In fret dressing, a luthier levels and polishes the frets, and crowns (carefully rounds and shapes) the ends and edges. Stainless steel guitar frets may never need dressing, because of the density of the material. Not having frets carefully and properly aligned with the fingerboard can cause severe intonation issues and constant detuning. The ultimate way of determining the source of a buzz and detuning problem is to measure the levelness of the frets. A straightedge positioned on the neck in the "lie" of one of the strings should show nearly level frets. (There should be a slight relief to compensate for the elliptical shape of the vibrating strings.)