Drum (container) in the context of "Barrel (unit)"

A lid or cover is part of a container, and serves as the closure or seal, usually one that completely closes the object. Lids can be placed on small containers such as tubs as well as larger lids for open-head pails and drums.

In mechanics, compressive strength (or compression strength) is the capacity of a material or structure to withstand loads tending to reduce size (compression). It is opposed to tensile strength which withstands loads tending to elongate, resisting tension (being pulled apart). In the study of strength of materials, compressive strength, tensile strength, and shear strength can be analyzed independently.

Some materials fracture at their compressive strength limit; others deform irreversibly, so a given amount of deformation may be considered as the limit for compressive load. Compressive strength is a key value for design of structures.

A closure is a device used to close or seal a container, such as a bottle, jug, jar, tube, or can. A closure may be a cap, cover, lid, plug, liner, or the like. The part of the container to which the closure is applied is called the finish.

Other types of containers, such as boxes and drums, may also have closures, but are not discussed in this article. Many containers and packages require a means of closing, which can be a separate device or seal, or sometimes an integral latch or lock.

A barrel bomb is an improvised unguided bomb, sometimes described as a flying IED (improvised explosive device). They are typically made from a large barrel-shaped metal container that has been filled with explosives, possibly shrapnel, oil or chemicals as well, and then dropped from a helicopter or aeroplane. Due to the large amount of explosives (up to 1,000 kilograms (2,200 lb)), their poor accuracy, and indiscriminate use in populated civilian areas (including refugee camps), the resulting impacts have been devastating. Critics have characterised them as weapons of terror and illegal under international conventions.

Barrel bombs were used in different conflict zones including in 1948 and by the US military in Vietnam in the late 1960s. Starting in the 1990s, they were also used in Sri Lanka, Croatia and Sudan. Barrel bombs were used extensively by the Syrian Air Force during the Syrian civil war—bringing the weapon to widespread global attention—and later by the Iraqi forces during the Anbar campaign. Experts believe they will continue to be embraced by unstable nations fighting insurgencies since they are cheap to make and utilise the advantages of a government's airpower.