Burial vaults or grave liners, also known as burial containers, are commonly used in "traditional," full-service funerals. The vault or liner is placed in the ground before burial, and the casket is lowered into it at burial.
The purpose is to prevent the ground from caving in. A grave liner is made of reinforced concrete and will satisfy any cemetery requirement. Grave liners cover only the top and sides of the casket. A burial vault is more substantial than a grave liner.
Burial vaults surround the casket in concrete or another material and may be sold with a warranty of protective strength.
State laws do not require a vault or liner, but many cemeteries require some type of outer burial container to prevent the grave from sinking in the future.
Neither grave liners nor burial vaults are designed to prevent the eventual decomposition of human remains.