When handle region(s) of disengaging lever(s) is/are pulled in direction(s) tending to cause disengagement of engagement between access-controlling body or bodies and main body housing(s), respective action edge(s) of rotating region(s) may rotate about shaft(s) in direction(s) tending to cause disengagement of engagement. Upon rotating in direction(s) tending to cause disengagement of engagement, respective action edge(s) of rotating region(s) may press on and impel support plate(s) of main body housing(s). In accompaniment thereto, disengaging lever(s) may move upward, and respective downwardly directed engagement projection(s) of access-controlling body or bodies may be lifted up and extricated from respective upwardly directed engagement projection(s) of main body housing(s). Moreover, when handle region(s) of disengaging lever(s) is/are pulled, respective sliding frame(s) of access-controlling body or bodies may move along respective guide rail(s) of main body housing(s) and toward exterior(s) of main body housing(s), greatly opening up access at opening(s) of main body housing(s).