Abstract: A closure (10) for a bag (not shown), such as a plastic bag for freezing shaped lumps of ice for cooling drinks, consists of a channel member (14) adapted to receive an insertion member (16). Before the insertion member (16) is pressed into the channel member (14), the end of the bag (not shown) is inserted between the two, being closed in a fluid-tight manner when the two members, in the example shown interconnected by a hinge (27), are pressed together.The closure makes it possible to close bags for freezing ice lumps in a fluid-tight manner, allowing the bags to lie down in a deep-freeze cabinet without leaking and also making it easier to open the bags than when these are closed by means of knots of the like.