A burial vault (also known as a burial liner, grave vault, and grave liner) is a container, formerly made of wood or brick but more often today made of metal or concrete, that encloses a coffin to help prevent a grave from sinking. Wooden coffins (or caskets) decompose, and often the weight of earth on top of the coffin, or the passage of heavy cemetery maintenance equipment over it, can cause the casket to collapse and the soil above it to settle.