lock and key, fastening fitted to an entryway, such as a gate or door, or a container, such as a cabinet, drawer or safe, to keep it closed and/or prevent unauthorized access or use. Locks typically consist of a sliding, pivoted, or rotary bolt protected by a fixed or movable object. A lock may be opened by a mechanical, magnetic, electric, electronic, or electromechanical key or by employing a code or sequence of numbers or letters.

Mechanical Locks

There are two basic types of mechanical locks, each with variations. The oldest and simplest is the warded lock, which is essentially a spring-loaded bolt in which a notch has been cut. The key fits into the notch and slides the bolt backward and forward. The lock takes its name from the fixed projections, or wards, inside the lock and around the keyhole. The correct key has notches cut into it that match the wards, which block the wrong key from operating the lock. The ward lock is the easiest to pick and now is used only for cheap padlocks.

The tumbler lock contains one or more pieces of metal (called tumblers, levers, or latches) that fall into a slot in the bolt and prevent it being moved. The proper key has serrations that raise the metal pieces to the correct height above the slot, allowing the bolt to slide. There are three types of tumbler locks, pin-tumbler, disk-tumbler, and lever-tumbler. Pin-tumbler locks are the most common. The tumblers in this type of lock are small pins. The modern door lock is a compact pin-tumbler cylinder lock of the type developed (1860) by the American inventor Linus Yale. Door locks on automobiles and most high-security locks have pin tumblers. Disk- or wafer-tumbler locks, use flat disks, or wafers, instead of pins. When the proper key is inserted, the disks retract, releasing the bolt. Disk-tumbler locks are often used in desks and file cabinets. Lever-tumbler locks employ a series of different-sized levers resting on a bolt pin to prevent the bolt from moving. When the proper key is inserted, all the levers are raised to the same height, enabling the bolt pin to release the bolt. Lever-tumbler locks are often used in briefcases, safe-deposit boxes, and lockers.

The first of the keyless locks was the combination lock, developed at the beginning of the 17th cent. In it a number of rings inscribed with letters or numbers are threaded on a spindle. To open the lock the rings must be turned to form a code word or number, which causes the slots inside the rings to align and permits the spindle to be drawn out. A variant of the combination lock employs a movable dial with a series of numbers around it in place of the rings. The dial must be turned clockwise and counterclockwise in the proper sequence of numbers to align disk tumblers and open the lock. Once used only for padlocks, combination locks began to be used in safes and strong-room doors during the last half of the 19th cent. The time lock, first used successfully c.1875, has a clock mechanism that is set to permit opening only a certain time.

Electric and Magnetic Locks

Recent lock developments include the magnetic-key lock, in which the pins are actuated by small magnets on the key, which has no serrations. When the key is inserted into the lock, these magnets repel magnetized spring-loaded pins, raising them in the same way that the serrations on a tumbler-type key would. The card-key lock is actuated by a series of magnetic charges; the card-key is popular where security is vital, because a new series may be electronically defined for each new user, without having to change the lock itself. Similarly, electronic card access systems are used in many hotels and office buildings. A special "key" system uses a paperboard or plastic card, on which a code is recorded as a series of holes or bumps, or a microchip or a magnetic strip on which a code is stored. A card reader at the lock location reads the code and sends the information to a computer, which sends a signal to release the bolt if the code is correct. Electronic combination locks similarly use a computer to compare a combination stored in memory with one entered on a keypad; access is permitted if the combinations match. In a biometric entry system the numeric keypad is replaced by a scanner, which captures an individual's fingerprint, palmprint, signature, or other personal characteristic and compares it with that in the computer's memory. Biometric entry systems are most often used in high-security areas, such as nuclear power plants.

In an electromagnetic lock a metal plate is attached to the door and an electromagnet is attached to the doorframe opposite the plate. When the current flows, the electromagnet attracts the plate, holding the door closed, When the flow of current is stopped, the door unlocks. A variation places the plate and electromagnet so that the door is held open when current flows, enabling the door to be closed automatically when the current stops.

Keyless entry systems, which are common in motor vehicles, rely on a keychain fob that contains a remote-control unit consisting of an integrated circuit and a radio transmitter. The fob sends a low-powered radio signal to a receiver in the motor vehicle, and, if the received code is the correct one, the receiver in the vehicle relays the signal to a microprocessor, which opens the lock. The acceptance of such entry systems has led to devices that allow additional functions within the vehicle to be activated remotely.

key, in mechanics: see lock and key.

key. 1 In music, term used to indicate the scale from which the tonal material of a given composition is derived. To say, for example, that a composition is in the key of C major means that it uses as its basic tonal material the tones of that scale which is associated with C major, and that its harmony employs the chords built on the tones of that scale. C is then the keynote, and the C major triad, or the notes CEG, the tonic chord of the composition. In addition to the seven tones of the C major scale, however, the remaining five tones of the chromatic scale may appear as auxiliary tones, and chords may be borrowed from other keys. Modulation to another key may take place, but if there is a return to the original key the whole composition is said to be in the key of C. At the beginning of a composition, its key is usually indicated by a key signature (see musical notation). A term usually used synonymously with key is tonality. Absence of a feeling of key is called atonality. The concept of keynotes was developed gradually during the 16th and 17th cent. and its partial or total abandonment was a feature of the modernism of the early and mid-20th cent. Polytonality, the employment of two or more keys simultaneously, has been used by some 20th-century composers. 2 Also in music, in reference to musical instruments the term key refers to a lever depressed by the player's finger or, in the case of the pedal keyboard of the organ, the foot. In woodwind instruments the keys control covers on the holes that shorten the vibrating column of air. In brass winds they control the valves that lower the pitch of the instrument by lengthening the tube.

Key, Francis Scott, 1779-1843, American poet, author of the Star-spangled Banner, b. present Carroll co., Md. A lawyer, he was U.S. attorney for the District of Columbia (1833-41). His works include The Power of Literature and Its Connection with Religion (1834) and the posthumous collection Poems (1857), which contains several hymns.

Key, Ellen, 1849-1926, Swedish author, critic, and ideologue. Believing that women are primarily fitted for motherhood, she deplored feminist claims to equality on the labor market. Her ideas regarding state child support influenced social legislation in several countries. Among her best-known works published in English are Love and Marriage (1911, repr. with critical and biographical notes by Havelock Ellis, 1931), The Century of the Child (1909), The Woman Movement (1912), The Younger Generation (1914), and War, Peace, and the Future (1916).

Key, David McKendree, 1824-1900, American politician and jurist, b. Greene co., Tenn. He practiced law in Chattanooga, Tenn., from 1853 to 1870, except during the Civil War, when he was an officer in the Confederate army. He served in the U.S. Senate (1875-77) to complete Andrew Johnson's term. In 1877, President Hayes chose Key to be his Postmaster General, an action that provoked sharp criticism from Republicans, who felt that the presence of an ex-Confederate in the cabinet violated party principles. From 1880 to 1894, Key served as U.S. judge for the eastern and middle districts of Tennessee.

Key West, city (1990 pop. 24,832), seat of Monroe co., S Fla., on an island at the southwestern extremity of the Florida Keys; inc. 1828. About 150 mi (240 km) from Miami (but only 90 mi/145 km from Cuba), it is the southernmost city of the continental United States. It is a port of entry and a cruise-ship stop, a popular resort with a tropical climate, a shrimping and fishing center, and an artists' colony. Tropical fruits are harvested, but tourism is central to the economy.

Early Spanish sailors called the site Cayo Hueso (Bone Island), because of the human bones they found there. A railroad (completed 1912) linked the Keys with the mainland. It was abandoned after being damaged by a hurricane in 1935 and was replaced by the 123-mi (198-km) Overseas Highway (completed in 1938). After a severe economic decline, the federal government took over (1934) the bankrupt city.

Places of interest include a sponge pier, an aquarium, a lighthouse (1846; replacing one built in 1825), Mallory Square (a daily sunset-viewing point), and two Civil War forts. John James Audubon and Winslow Homer painted in Key West, and the city was used as a setting in the works of Ernest Hemingway, who once lived there. His home (built 1851) was made a museum, as was the Little White House, President Harry S. Truman's personal retreat.

Key Largo, narrow island, c.30 mi (48 km) long, off S Fla., largest of the Florida Keys. Along with other Florida Keys, especially Key West, it has become an increasingly popular tourist spot, noted for its scuba diving, nightlife, and beachside resorts. Housing developments and shopping complexes have been recently constructed. A major attraction is John Pennekamp Coral Reef State Park, the first underwater park in the United States, containing c.78 sq mi (202 sq km) of living coral and hundreds of varieties of marine life. Also offshore is the Aquarius habitat, the National Oceanic and Atmospheric Administration's permanent undersea laboratory.

Key Islands: see Kai Islands, Indonesia.

In music, the sharps or flats placed on the staff to indicate the key for a composition or a section. Placement of the symbols on lines and spaces indicates which notes are to be altered by the sharps or flats; for example, a sharp on the top line of the treble clef governs every F on the staff and indicates the key of G major or E minor. Each set of major and minor keys is designated with a particular grouping of sharps or flats.

Learn more about key signature with a free trial on Britannica.com.

In music, system of pitches and harmonies generated from a scale of seven tones, one of which is predominantly important. Keys are a basic element of tonality and represent an outgrowth of modal music (see church mode). When a given piece is said to be “in C,” C is its “tonic,” or central tone. Most Western music from about 1700 until about 1900 is characterized by use of the 12 major and 12 minor keys of the tonal system.

Learn more about key with a free trial on Britannica.com.

(born Aug. 1, 1779, Frederick county, Md., U.S.—died Jan. 11, 1843, Baltimore, Md.) U.S. lawyer, author of “The Star Spangled Banner.” After the burning of Washington, D.C., in the War of 1812 he was sent to secure the release of a friend from a British ship in Chesapeake Bay. He watched the British shelling of Fort McHenry during the night of Sept. 13–14, 1814; when he saw the U.S. flag still flying the next morning, he wrote the poem “Defense of Fort M'Henry.” Published in the Baltimore Patriot, it was later set to the tune of an English drinking song, “To Anacreon in Heaven.” The song was adopted as the U.S. national anthem in 1931.

Learn more about Key, Francis Scott with a free trial on Britannica.com.

(born Jan. 27, 1824, Greene county, Tenn., U.S.—died Feb. 3, 1900, Chattanooga, Tenn.) U.S. politician. Admitted to the bar in 1850, he practiced law in Chattanooga and became active in Democratic Party politics. He opposed secession by the South but served in the Confederate army during the American Civil War, rising to the rank of lieutenant colonel. After the war he worked to heal sectional grievances and restore the Union. He was appointed to the U.S. Senate (1875), succeeding former president Andrew Johnson, but two years later was defeated in a bid to retain the seat. When the disputed 1876 presidential election was turned over to a special Electoral Commission, the Republican candidate, Rutherford B. Hayes, secured the support of Southern Democrats by promising, among other things, to appoint a Southerner to his cabinet. Key was thus appointed postmaster general in 1877. From 1880 to 1894 Key was a U.S. district judge in Tennessee.

Learn more about Key, David M(cKendree) with a free trial on Britannica.com.

City (pop., 2000: 25,478), southwestern Florida, U.S. The southernmost city of the continental U.S., it lies on an island about 4 mi (6.5 km) long and 1.5 mi (2.4 km) wide in the western Florida Keys. The name is an English corruption of Cayo Hueso (“Bone Islet”), as it was called by Spanish explorers who found human bones there. In 1822 a U.S. naval depot was set up on Key West as a base of operations against pirates. Now a winter resort, Key West is also a tourist destination. Many writers and artists have lived there, and the homes of Ernest Hemingway and John James Audubon have been preserved.

Learn more about Key West with a free trial on Britannica.com.

(born Sept. 24, 1896, St. Paul, Minn., U.S.—died Dec. 21, 1940, Hollywood, Calif.) U.S. novelist and short-story writer. Fitzgerald attended Princeton University but dropped out with bad grades. In 1920 he married Zelda Sayre (1900–48), daughter of a respected Alabama judge. His works, including the early novels This Side of Paradise (1920) and The Beautiful and Damned (1922) and the story collections Tales of the Jazz Age (1922) and All the Sad Young Men (1926), capture the Jazz Age's vulgarity and dazzling promise. His brilliant The Great Gatsby (1925; film, 1926, 1949, 1974; TV movie 2001), a story of American wealth and corruption, was eventually acclaimed one of the century's greatest novels. In 1924 Scott and Zelda became part of the expatriate community on the French Riviera, the setting of Tender Is the Night (1934; film, 1962). His fame and prosperity proved disorienting to them both, and he became seriously alcoholic. Zelda never fully recovered from a mental breakdown in 1932 and spent most of her remaining years in a sanitarium. In 1937 Scott moved to Hollywood to write film scripts; the experience inspired the unfinished The Last Tycoon (1941; film, 1976). He died of a heart attack at age 44.

Learn more about Fitzgerald, F(rancis) Scott (Key) with a free trial on Britannica.com.