(n) A hollow mandrel fitted with swab cups used for swabbing. v. to operate a swab on a wireline to lower the pressure in the well bore and bring well fluids to the surface when the well does not flow naturally. Swabbing is a temporary operation to determine whether the well can be made to flow. If the well does not flow after being swabbed, a pump is installed as a permanent lifting device to bring the oil to the surface