A solution treatment apparatus of the present invention includes a diaphragm position varying mechanism configured to partly vary the position of a diaphragm. The method further comprises inserting a portion of the fastener member into the first interface. A third annular support assembly is to be coupled to the rotating shaft between the first and second support assemblies. A substantially planar spring having two curved sections is used to join the shafts through the corresponding coupling sections. Furniture panel can be connected by inserting the middle buckle into the female buckle and inserting the sub-buckle into the middle buckle without using a tool, facilitating the assembly of the furniture.