wood
Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...
en or
plastic
Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...
casks
A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids ...
. It is found on the curved side of the cask, arranged so that when the cask is on its side and the keystone is at the lowest part of the rim, the shive will be the highest point of the cask.
The hole in that part of the cask is used for two purposes. Firstly, it is used for cleaning out and then refilling the cask, which requires a large hole. Once the cask arrives at its destination, the hole is used to control the amount of
carbon dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
present in the container, which requires a small hole. The shive is effectively an adaptor that reconciles these conflicting requirements. It is a wooden disk, larger than a keystone, that fits in the hole in the cask and has a smaller hole in its centre.
For washing and filling, the old shive is removed using a chisel or a special tool, revealing a hole around 3
inch
The inch (symbol: in or prime (symbol), ) is a Units of measurement, unit of length in the imperial units, British Imperial and the United States customary units, United States customary System of measurement, systems of measurement. It is eq ...
es (7.5 cm) across. Once the cask has been filled and fined, a new shive is
hammer
A hammer is a tool, most often a hand tool, consisting of a weighted "head" fixed to a long handle that is swung to deliver an impact to a small area of an object. This can be, for example, to drive nail (fastener), nails into wood, to sh ...
ed into place. The hole in the centre of the shive will be sealed with a small wooden or plastic peg. The cask is then transported to the pub.
Some time before the beer is to be served (two or three days is common; especially strong beers may require more) the cask is opened or "vented". This entails breaking the seal in the middle of the shive by punching it through into the cask with a
mallet
A mallet is a tool used for imparting force on another object, often made of rubber or sometimes wood, that is smaller than a maul or beetle, and usually has a relatively large head.
General overview
The term is descriptive of the ...
and some kind of tool, usually just a hard spile.
A spile is then placed in the hole to regulate the gas flow. If the beer is particularly "lively" (common in warm weather and with specific beers) the contents may spray out when the cask is vented.
During use, the hole in the centre of the shive can also be used (with the spile removed) to insert a marked dipstick in order to measure the quantity of beer remaining.
As with keystones, it is considered good form to close up the hole in the shive when returning empty casks, both to prevent spillage and to reduce bacterial and fungal contamination.