Further, a distance between the two flanged bosses 113A, 113B is larger than a distance between the two quick-release hole portions 2122 of the two quick-release guide rails 212A, 212B. Therefore, as shown in FIGS. 9 and 10, the two flanged bosses 113, 113B would not simultaneously disengage from the two quick-release guide rails 212A, 212B. Preferably, on the quick-release guide rail 212B, the quick-release hole portion 2122 is arranged at a front end of the rail portion 2121, i.e. a point on the quick-release guide rail 212B that is closest to the second pivot section 122; and on the quick-release guide rail 212A, the quick-release hole portion 2122 is arranged at a point on the rail portion 2121 that is located behind the front end of the rail portion 2121 by a predetermined distance. Accordingly, when the pulling member 110 is pulled outward relative to the first partitioning wall 210, the flanged boss 113A will reach at the quick-release hole portion 2122 of the quick-release guide rail 212A first, allowing the flange portion 1132 of the flanged boss 113A to move out of the quick-release hole portion 2122 of the quick-release guide rail 212A. Thereafter, when the pulling member 110 is further pulled outward for the flanged boss 113B to reach at the quick-release hole portion 2122 of the quick-release guide rail 212B, the flange portion 1132 of the flanged boss 113B can be easily disengaged from the quick-release hole portion 2122 of the quick-release guide rail 212B, allowing the pull-out aiding device 100 to be fully detached from the first partitioning wall 210.