Core drilling involves use of a core barrel, attached at the bottom of a string of rods, which is rotated and advanced through soil or rock to obtain a core sample of the material. Water or drill fluid is used to cool the cutting bit and to carry cuttings to the surface. There are two types of core drilling: conventional and wire line. To retrieve a core cut with a conventional core barrel, the entire string of drill rods must be removed from the hole. The wire line core barrel has an inner barrel which holds the core that can be pulled up through the drill rods thereby eliminating the need to remove the entire string of drill rods