A packoff is located within a wellhead housing and a casing hanger. The packoff has an internal ratchet ring that engages a threaded profile on the exterior of the casing hanger thereby allowing installation of the packoff to be achieved by simply stabbing the packoff over the protruding neck of the casing hanger. This ratchet ring significantly reduces the rotation required during installation, decreasing potential for damage to seals. The casing hanger has an external lock ring that is inwardly biased. During installation of the packoff, the packoff acts to activate the lock ring to thereby force it outward. The lock ring is forced outward and into a recess formed in the interior of the wellhead housing. The lock ring and the ratchet ring locks the packoff and casing hanger into place with the wellhead housing without the need of external lockdown screws, thereby minimizing leak paths.