To provide easier sliding movement of partition boards on rails, together with much more presentable appearance by setting the rail invisible.

A channel 51 with an opening 51a on its back 5a is put so as to meet a rail 5 made on the header on back of a shelf 3. A slider 7 is set in the Channel 51 so that it runs horizontally in the channel. A partition board 4 is put through the gap between the rail 5 and a back board 2. An arm holder 6 put on the back 4a of the partition board 4 is connected to the slider 7 so as that the bottom 62 and the board 4 meet on the hole 51a of the channel 51. The partition board 4 is thus made to slide horizontally on the shelf 3.