Disclosed herein are, amongst other things, a molding apparatus with which to mold, in use, a preform of a type for blow molding into a container. The molding apparatus includes a lock ring (104, 204) for use in a first stack portion (108) of a mold stack (120). The lock ring (104, 204) includes a tubular body (150, 250) that is configured to define, amongst other things, a support interface (194) in cooperation, in use, with a split insert (6, 106) of the first stack portion through which a compressive load is transferrable during molding of the preform, wherein the support interface (194) includes a support shelf (154) that is defined, at least in part, on a first major promontory (152, 252) of the tubular body (150, 250).