Abstract: A mold-locking or catching device which comprises a support on one mold half or part, a bellows anchored to this support at one side of the bellows, a hook engageable with the rim of the other mold half or part and carried by the other side of the bellows and means for swinging the hook laterally into and out of engagement with the rim of the other mold half when the bellows is activated by fluid pressure or depressurized respectively.