To facilitate and ensure fixture of a lower slab, a core shaft, and a lower ornamental railing end to each other.

The lower slab 2 includes a cylinder portion 2A which has an engaging groove 4 formed in an internal peripheral surface 2a thereof in the vicinity of its lower portion. The lower ornamental railing end 5 has a shaft accommodating recess 5A with its upper end opened, and a fitting portion 5B of the lower ornamental railing end 5 is press-fitted into a lower end of the cylinder portion 2A. Then, the core shaft 7 for pivoting the upper slab 3 is press-fitted into the shaft accommodating recess 5A of the lower ornamental railing end 5. Further, an engaging portion 8 which radially outwardly protrudes and engages with the engaging groove 4 is formed on an upper portion of the fitting portion 5B of the lower ornamental railing end 5.