The standard guitar has six strings, but four-, seven-, eight-, nine-, ten-, eleven-, twelve-, thirteen- and eighteen-string guitars are also available. Classical and flamenco guitars historically used gut strings, but these have been superseded by polymer materials, such as nylon and fluorocarbon. Modern guitar strings are constructed from metal, polymers, or animal or plant product materials. Instruments utilizing "steel" strings may have strings made from alloys incorporating steel, nickel or phosphor bronze. Bass strings for both instruments are wound rather than monofilament.
The top, back and ribs of an acoustic guitar body are very thin (1–2 mm), so a flexible piece of wood called lining is glued into the corners where the rib meets the top and back. This interior reinforcement provides 5 to 20 mm of solid gluing area for these corner joints. Solid linings are often used in classical guitars, while kerfed lining is most often found in steel string acoustics. Kerfed lining is also called kerfing because it is scored, or "kerfed"(incompletely sawn through), to allow it to bend with the shape of the rib). During final construction, a small section of the outside corners is carved or routed out and filled with binding material on the outside corners and decorative strips of material next to the binding, which are called purfling. This binding serves to seal off the end grain of the top and back. Purfling can also appear on the back of an acoustic guitar, marking the edge joints of the two or three sections of the back. Binding and purfling materials are generally made of either wood or plastic.
SFCM produces some of the most successful and influential classical guitarists in the world. Spearheaded by renowned faculty and complemented by visiting artists such as Marcin Dylla, the department honors the tradition of the classical guitar while cultivating innovation. The Harris Guitar Collection, housed at SFCM, gives students a chance to see—and play—some of the most extraordinary guitars of the last two centuries.