Therefore, when the dummy chassis 10 is pushed into the accommodation space 414 along the sliding rails 430 of the certain sliding rail set 420, the dummy chassis 10 is located at the front end 411 and the rear end 412 of the rack body 410 at the same time. More specifically, the first frame bar 100 occupies the position of the front end 411 of the rack body 410, and the second frame bar 200 covers the corresponding one of the power sockets 441.

Thus, through the construction of the embodiments above, since the dummy chassis 10 is moved into a configuration space of the certain layer in the rackmount chassis without receiving the server unit, because the dummy chassis 10 is located at the front end 411 and the rear end 412 of the rack body 410 at the same time, not only the possibility of the maintenance personnel accidentally touching the power socket 441 of the certain layer to be injured can be decreased, but also the preset airflow path in the server rack 400 can be maintained, and the degree of dust or foreign objects intrusion can be reduced.