A top closure obturating panel (2) of a carton is formed with a partial depth cut (4) in the form of an open loop of which one end (4a) is at a greater distance from a central zone of the loop (4) than is the other end (4b). Following filling and top-sealing of the carton, there is applied to the panel (2) a pour spout fitment consisting of a flanged pour spout, a screw cap on the pour spout, and a plunger co-operating with the screw cap and the pour spout in such manner that, upon unscrewing of the screw cap, the plunger screws inwards. At its inner end, the plunger is formed with arcuate pushing blades (6), which thereby cause the laminate material of the panel (2) to fracture along the partial depth cut (4) such that an encircling portion (2a) of the panel (2) and an encircled portion (2b) within the loop (4) separate from each other along the loop (4), but remain interconnected by way of an intermediate portion (2c) extending through between the ends (4a) and (4b) of the loop (4).