Abstract: The invention relates to a pressure closing device for joining the edges of plastic sheets, comprising a shaped strip fastened by heat-sealing in the vicinity of each of the edges to be joined, each of the strips comprising a hooking element able to work with the corresponding hooking element of the shaped strip fastened in the vicinity of the other edge to be joined and a flap by which the shaped strip is fastened to the corresponding sheet.The flap of each shaped strip has at least one intermediate longitudinal rib protruding from one of its faces.