Based on the quantity and heights of the server devices, the position of each rail 14 relative to the panel 11 can be adjusted by selecting one of the coupling recesses 111b at suitable height for attachment of the coupling portion 141 of the rail 14. As the height of each rail 14 on the panel 11 is adjustable, the height of the gap 142 between two adjacent rails 14 is also adjustable to suit the height of a server device to be installed. As the number of the rails 14 assembled on the panel 11 may be varied, the quantity of server devices to be installed may also be varied. Therefore, the multiusability of the existing cabinet 9 can be enhanced.