Casing hangers are devices that allow casing to be set in the well bore during the drilling phase of an oil or gas well. There are two basic designs of casing hanger, slip-type or mandrel. The slip-type is the conventional and most commonly used. The mandrel-type is normally used when special needs arise during the building of the well. Both allow for the Tens of Thousands of pounds in weight of the casing string weight to be transferred from the derrick of the drilling rig to the load shoulder in a casing head or spool. A Casing Hanger performs the following functions: