A container-closure assembly comprising a container having a nozzle portion with a puncturable diaphragm defining a discharge opening an a closure including a piercing portion of generally cup-like form positionable over the nozzle and having a piercing element;

a plurality of axially extending circumferentially spaced ribs of generally square cross section on the exterior surface of the nozzle portion and a plurality of circumferentially spaced grooves of generally square cross section on the interior wall of the piercing portion to provide interengaging guide means when applying the piercing portion over the nozzle portion to pierce the diaphragm;
the outer surface of the piercing portion being knurled to provide a gripping means; and
the knurling being interrupted at circumferentially spaced locations aligned with the grooves on the interior surface of the piercing portion to facilitate alignment of the grooves with the ribs on the nozzle portion when applying the closure to the container.