The strings are supported by detachable bones at the nut and bridge (see illustration). The nut bone, which is slightly grooved to provide a guide for each string, sets the height above the fingerboard at that end. If the strings are too low they will buzz against the frets. If they are too high, the guitar becomes hard to play, which can completely discourage you from continuing.

If the setting is too high, the nut bone needs to be removed and filed down from the underside.If it is too low, a sliver of cardboard or similar material may be inserted underneath, but this should be a temporary solution until a new bone of the right height can be obtained. On a classical guitar the height of the strings at the first fret will be about 1/16 in (1.5 mm).

At the bridge end, a similar adjustment can be made to the bridge bone to produce a height at the twelfth fret of approximately 3/16 in (5 mm). The reason the measurements are approximate is that the exact amount depends on the height of the frets and the total string length, both of which vary from maker to maker.

Note that these measurements are for the nylon string guitar. The metal strings of the acoustic guitar are set lower due to the greater tension, and for the sake of the left hand, steel strings need to be as low as is practical, consistent with clear sound.