To improve connecting strength by fitting a spacer to a partition panel in such a manner to be disabled from shifting in the direction of thickness, and providing a clamp device with a hook hung on the inner surface of the upper end part of a support and with a rotary lever for drawing the hook toward the partition panel.

With a spacer 8 interposed between a support 1 and a partition panel 2, the upper end of the partition panel 2 and the upper end of the support 1 are drawn to each other by a clamp device 7. A support block 28 is fitted to a lever 29, and a first pin 31 is passed through the base end of a hook 27. When a lever 29 is let down and turned, a hook part 27a of a hook 27 is moved to approach a locking means 30. The support 1 is drawn to the partition panel 2 by moving the hook 27 backward. When a second pin 39 passed through the lever 29 is fitted in a notch groove of an upward opening formed in the locking means 30 from above, the lever 29 is kept in the state of being let down and turned.