PURPOSE: To enable a containing body to be mounted in a well-contained state in a state to be positioned aside from a beam even when the beam is mounted in a state to protruded from a ceiling surface by a method wherein a gantry type front frame protruded from the upper front end of the containing body is situated between a ceiling surface and the containing body, and a gantry type stuffing frame is located between the front beam and a beam.

CONSTITUTION: When a containing body 4 is mounted between a ceiling surface 1 and a floor surface 3, namely when it is mounted between the ceiling surface 1 in a state that a beam 2 is protruded from the ceiling surface 1 and a floor surface 3, the beam 2 is positioned in a notch part 8, and a stuffing frame 6 is situated between the beam 2 and a front frame 5. The containing body 4 is mounted below the beam 2, and the upper part of the containing body 4 is contained in a well-contained state in a state to be positioned aside from the beam 2. When the width of the beam 2 is different, by reducing the stuffing frame 6 in a way to cut the stuffing frame 6, the upper part of the containing body 4 can be mounted in a well-contained state in a state to be positioned aside from the beam 2. Further, a containing space can be ensured above the containing body 4 in a state to be positioned aside from the beam 2 by means of the stuffing frame 6 and the front frame 5.