A drum is a cylindrical container used for shipping bulk goods. Drums can be made of steel, dense paperboard (Commonly called Fiber drums — See Footnote) or plastics, and are generally used for the transportation of certain dangerous materials or modest quantities of bulk goods. For caustic and acid materials, plastics, usually thermoplastics like Nylon, Polystyrene, Polyvinyl chlorides (PVCs) or possibly Polycarbonates are the preferred shipping container; for flammable substances like most petroleum distillates, and alcohol, etc., metal containers are the standard. Which type is used for shipping non-corrosive industrial chemicals would depend on the chemicals or materials, but the general rule would be to use the container type that is inert or non-reactive with the material being shipped.It is common to hear a drum referred to as a barrel in the United States, and some would argue that barrels hold liquids while drums are open topped (see British 44 gallon drum), but in every day USA style English usage, the two terms are used near interchangeably in the vernacular. Drums such as these have a standard nominal volume of 55 US gallons (44 Imperial gallons) and nominally measure just under 34-1/2" tall with a diameter just under 24" and differ by holding about thirteen gallons more than a Barrel of Crude Oil one hears about (the quoted price of) in the daily financial news reports. In the US, 25 gallon drums are also in common use and have the same height specification. This sameness allows easy stacking of mixed pallets. Taking account the materials making up the drum, in the vernacular, these three main varieties are known as plastic drums or barrels, cardboard Drums or barrels and steel drums or barrels.The two common sub-types of drums are the open top and the welded top (with 2” bung holes). The later are almost universally called 'barrels' in preference to drums in the US. They cannot efficaciously either dispense or be filled with powdered goods, though they might store them very well, so are not used for such goods, being reserved for liquids transport and storage. Plastic drums are manufactured using injection blow moulding technology. Metal drums are hot rolled into long pipe-like sections then Forged on a Stamping Press while still red hot into drum bodies. A welded rolled seam, is then made for the drum bottom, or bottom and top both.Standard drums have reinforcing rings of thickened metal or plastic at four places: Top, Bottom, and one each a third of the way from each end ring. This sufficiently strengthens them so that they can be readily be turned on their sides and rolled when filled with heavy materials, like liquids. Over short to medium distances, drums are generally tipped and rolled on the bottom rim while being held at an angle, balanced, and rotated with a two handed top grip that also supplies the torque (rotational or rolling force).The open top sub-type is sealed by a mechanical ring clamp (concave inwards) that exerts sufficient pressure to hold many non-volatile liquids and make an air tight seal against a gasket, as it exerts force inward and downward when tightened by a normal three-quarter inch wrench or rachet wrench. Tops exist with bung holes as above, and these hybrid drums cum lid can be used to ship many non-volatile liquids as well as industrial powders. Many drums are used to ship and store powdered products as well as liquids, such as plastic beads for injection moulding, extrusion, and purified industrial grade powders like cleansers (e.g., fertilizers, and powdered aluminum). If used to transport dangerous goods across international boundaries, they may need to have UN certification. In general, drum usage is limited to wholesale distribution of bulk products, which are then further processed or sub-divided in a factory.Today's 55 gallon drum resulted from military shipping requirements and specifications circa World War I, the first modern war where trucks, cold rolled steel, stamp or pattern forging machinery and welding were widely available making mass produced standardized shipping containers feasible. The 55 gallon drum will fit handily four to a fork truck standard wooden shipping pallet and so greatly ease material handling and rapid shipping. The drums size, shape, and weight distribution lends itself readily to being moved about readily on the loading dock or factory floor with a two wheeled Hand Truck.The now ubiquitous welded top steel drums played a vital strategic role in the first United States strategic offensive in the South Pacific Theater during World War II, in particular, though a huge part of the allied effort on all fronts. This happened because neither side could maintain Control of the Seas (or SLOC - Sea Lines of Communications) during the Battle of Guadalcanal (7 August 1942 - 9 February 1943); The Japanese Navy was held to night operations because the Marine Aviators on the island could bomb by day keeping the stronger Japanese fleet at arms length, but only because of the lowly fuel drum. The much needed aviation fuel was off-loaded from ships (frequently as deck cargo on fast ships like destroyers) in the daylight using the technique of off loading the barrels by simply shoving them over the sides (or time permitting, lowering them in cargo nets), where they were corralled and pulled to shore by navy Seabees in a variety of small craft. Aviation fuel is significantly lighter than seawater so the drums floated allowing this expedience. Normal freight handling would have taken too long to sustain the aircraft on Guadalcanal, dubbed by the colorful moniker, The Cactus Airforce. This freed up precious time and resources, for the most part, to offload and land less compliant goods lower priority goods and materials like food, weapons, medicines, et al. For months while new construction gradually augmented the allied naval strength, the allied ships would pull out again as night fell - when the Tokyo Express ran in reinforcements for the Japanese under strong naval escort.