Abstract: Self-closing, snap-open pouch or sack type of flexible container having closure emore transversely flexible in one direction than in the other under longitudinal load and/or more outwardly flexible at or toward its center than at its ends. Opposed transverse creases adjacent the ends of each closure strip insure that the strips will spring apart under a longitudinal compressive load applied substantially to both strips. The walls of the containers are made from sheet material with a pair of closure strips secured to the sheet margins; longitudinal center folding of the sheet brings the closure strips into opposed juxtaposition and allows the folded sheet to be severed and end-sealed to form individual containers and place the ends of one closure element in a pivotal relationship with the ends of an opposite closure element.