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A sandbag is typically used in flood control, but the exact use can vary.

Sandbags are burlap bags filled with sand or soil, in an amount that a person can carry from where it is filled, to where it will be used. The use most people are familiar with is water control during emergencies, when rivers are threatening to flood outside their normal channel, or if a levee or dike is damaged. However, sandbags often are used in non-emergency situations (or after the emergency has passed) as the foundation for new (or just higher) levees, or other water-control structures.

In military science, sandbags are also used for field fortifications, or as a temporary protective measure for civilian structures. Because burlap and soil are very inexpensive, quite thick protective structures can be erected cheaply. The friction generated between moving soil or sand grains, and the multiple tiny air gaps, also make sandbags quite efficient dissipators of explosive blast. Sandbags used in fortification generally have dimensions carefully calculated so that the finished bags can be interlocked like brickwork, and are of such a weight as to maximise the efficiency of manual labour in filling and laying them. They may be laid in excavated defences as revetment, or as free-standing walls above ground where excavations are impractical. Plain burlap sandbags deteriorate fairly quickly, so if it is anticipated that a sandbag structure will remain in place for a long time, it may be painted with a portland cement slurry to reduce the effects of rot and abrasion.

Sandbags are also used for disposable ballastBallast may mean: railroad or railway ballast: gravel or cinders forming the track-bed on which sleepers (ties) and track is laid, for proper drainage a ship's ballast: water, sand, rocks, or bricks used to weight it down when it has very little cargo (th in hot air balloonHot air balloons are the oldest successful human flight technology, dating back to the Montgolfier brothers' invention in Annonay, France in 1783. The first manned flight was made on November 21, 1783, in Paris by Pilatre de Rozier and the Marquis d'Arlans, and as counterweightA counterweight is a weight that balances a load. You see them on lifts, cranes, and funfair rides. If the counterweight were not there, the load would tend to tip the crane forwards [clockwise]. The counterweight, which is usually made of a dense materias for theatre setsIn drama, the set (or setting is the location of a story's "action. Set construction is the department of theatrical production that concerns itself with the fabrication of scenery. Such theatrical sets are used in live stage plays, opera, and in movie an.

Historically, sandbags have typically been filled manually by people wielding shovelA shovel is a tool for lifting and moving loose material such as coal, gravel, snow, dirt, or sand. It is usually a hand tool consisting of a broad blade with edges or sides that is fixed to a medium-length handle. The term "shovel" is also applied to lars, although machineA machine is any mechanical or electrical device that transmits or modifies energy to perform or assist in the performance of tasks. It normally requires an input as a trigger, and transmits the modified energy to an output, which performs the desired tass able to fill bags at a much greater rate have been in use since the 1990sCenturies: 19th century 20th century 21st century Decades: 1940s 1950s 1960s 1970s 1980s 1990s 2000s 2010s 2020s 2030s 2040s Years: Events and trends Computers, technology Explosive growth of the Internet; decrease in the cost of computers and other techn.

Sandbag can also refer to a crude weapon consisting of a small bag filled with sand for use as a cudgel typically by criminals, or to the act of striking a person on the head with such a weapon. This usage is obsolescent in normal speech, appearing mainly in legal codes. However the verb form is extended metaphorically in several slang expressions.