To fold and build up a container by a light force, and surely prevent the flyer plate from turning when the containers are stacked by a method wherein at the turning base part of the flyer plate, an engaging groove of which the upper frame direction is open, is provided, and on the upper frame corresponding with the engaging groove, a lock member which enters the inside of the engaging groove when moving downward, is provided.

When this container is built up and stacked at the time of usage a lock member 12 is pressed downward by a grounding rib 2a of an upper container, and the lower end of a lock part 15 sticks out and enters an engaging groove 11 of a flyer plate 6, and a locked state is presented, and the turning of the flyer plate 6 is restricted by the engagement between the lock part 15 and the engaging groove 11, and the flyer plate 6 is prevented from turning. In the meantime, when the load from the top is removed, the lock part 15 moves upward by the elasticity of an elastic supporting part 14, and a state wherein the engaged state between the lock part 15 and the engaging groove 11 is released, is kept, and the engaging groove 11 and the lock member 12 do not obstruct the turning of the flyer plate 6 at the time of building up and the folding of the container, and the folding and the building up can be performed by a light force.