A bracket device (26, 200, 300), comprising: a side wall; a mounting member configured to penetrate through a post of a rack arranged adjacent to the side wall, the mounting member having a first vertex; and a fastening member (42, 201, 301) configured to lock the bracket device to a post movable relative to the side wall and configured to be located at a locking position, the fastening member (42, 201, 301) comprising a supporting part (52, 202, 302), the supporting part (52, 202, 302) having a second vertex (54, 204, 304); wherein the fastening member (42, 201, 301) further comprises a longitudinal part and a transverse part (60, 206, 306) bent relative to the longitudinal part, the supporting part (52, 202, 302) is extended a first predetermined distance from the transverse part (60, 206, 306) along the longitudinal direction, characterized in that: the second vertex (54, 204, 304) of the supporting part (52, 202, 302) and the first vertex of the mounting member are configured to be substantially located at a same longitudinal position along a longitudinal direction, when the fastening member (42, 201, 301) is located at the locking position, such that the second vertex (54, 204, 304) of the supporting part (52, 202, 302) of the fastening member (42, 201, 301) is configured to abut against an ear part of a carried object, wherein the fastening member (42, 201, 301) further comprises an extension wall extended a second predetermined distance from the transverse part (60, 206, 306) along the longitudinal direction, the second predetermined distance is smaller than the first predetermined distance, and the extension wall is connected to the supporting part (52, 202, 302). a side wall; a mounting member configured to penetrate through a post of a rack arranged adjacent to the side wall, the mounting member having a first vertex; and a fastening member (42, 201, 301) configured to lock the bracket device to a post movable relative to the side wall and configured to be located at a locking position, the fastening member (42, 201, 301) comprising a supporting part (52, 202, 302), the supporting part (52, 202, 302) having a second vertex (54, 204, 304); wherein the fastening member (42, 201, 301) further comprises a longitudinal part and a transverse part (60, 206, 306) bent relative to the longitudinal part, the supporting part (52, 202, 302) is extended a first predetermined distance from the transverse part (60, 206, 306) along the longitudinal direction, characterized in that: the second vertex (54, 204, 304) of the supporting part (52, 202, 302) and the first vertex of the mounting member are configured to be substantially located at a same longitudinal position along a longitudinal direction, when the fastening member (42, 201, 301) is located at the locking position, such that the second vertex (54, 204, 304) of the supporting part (52, 202, 302) of the fastening member (42, 201, 301) is configured to abut against an ear part of a carried object, wherein the fastening member (42, 201, 301) further comprises an extension wall extended a second predetermined distance from the transverse part (60, 206, 306) along the longitudinal direction, the second predetermined distance is smaller than the first predetermined distance, and the extension wall is connected to the supporting part (52, 202, 302). the second vertex (54, 204, 304) of the supporting part (52, 202, 302) and the first vertex of the mounting member are configured to be substantially located at a same longitudinal position along a longitudinal direction, when the fastening member (42, 201, 301) is located at the locking position, such that the second vertex (54, 204, 304) of the supporting part (52, 202, 302) of the fastening member (42, 201, 301) is configured to abut against an ear part of a carried object, wherein the fastening member (42, 201, 301) further comprises an extension wall extended a second predetermined distance from the transverse part (60, 206, 306) along the longitudinal direction, the second predetermined distance is smaller than the first predetermined distance, and the extension wall is connected to the supporting part (52, 202, 302).