A mold comprising a first mold element and a second mold element releasingly engagable between an open position and a closed position to define a mold cavity in the closed position and a first part line between the first mold element and second mold element. The first mold element comprises a first mold portion and a second mold portion configured to be reversible separable with respect to one another to define a second part line therebetween disposed interiorly with respect to a periphery of the first part line. At least one vent is disposed in the second part line. In one embodiment, the at least one vent comprises a passageway configured to permit mold material in the mold cavity to enter but not to exit the passageway to cause at least partial curing of the mold material in the passageway.