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 as the casket deteriorates over time. 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.