To stably fit left and right blades to a thin pillar to prevent danger by supporting left and right blades with one center blade, and supporting a shelf board or the like with a hinge.

For example, when the interior of a wall is made into a storage space, a shaft L is inserted into blades A, B, C and washers G, E, F, and the blade B and the shaft L are fixed together. Next, the left and right shelf boards of a pillar 1 are up and down opened/closed by one hinge. In this case, the pillar 1 is made of thin metal, and danger at opening-closing is prevented by springs H, H'. Further, optional spaces are set by the thickness of the washers E, F to smoothly open/close. and the blades A, C are stabilized by the length of the shaft L. Falling from the vertical to over about 38 degees is prevented. Hereby the blades A, B, C are stabilized, and danger can be prevented by the action of the springs H, H'.