A supporting assembly (200, 300), comprising: a first bracket (204, 304) including a first end portion and a second end portion; a supporting frame (202, 302) connected to the first bracket (204, 304) at a position adjacent to the second end portion of the first bracket (204, 304), wherein the supporting frame (202, 302) has a first supporting section (214, 310); and a second bracket (220, 318); one of the first bracket (204, 304) and the supporting frame (202, 302) is provided with a second supporting section (206, 306), and the first supporting section (214, 310) and the second supporting section (206, 306) jointly constitute a supporting channel (207, 316) for supporting the second bracket (220, 318), wherein the supporting frame (202, 302) is a separate component connected to the first bracket (204, 304), wherein the first bracket (204, 304) has a first lateral side and a second lateral side, and the first lateral side is provided with a carrying portion (62, 216) for carrying an external object, the first supporting section (214, 310) is located on the second lateral side, and the second supporting section (206, 306) is located on the second lateral side, the carrying portion is arranged on the first lateral side of a sidewall of the first bracket, is substantially adjacent to the a lower portion of the side wall, and extends in a first direction (Dl), the carrying portion is configured to carry a bottom portion of the external object in such a way that a lateral side of the external object is configured to be pressed against and thereby supported by the first lateral side of a sidewall of the first bracket, the first supporting section and the second supporting section extend in a second direction that is different from the first direction, and wherein the sidewall (38, 208) of the first bracket (204, 304) has a first feature (54, 320), the sidewall (48, 226) of the second bracket (220, 318) has a second feature (56, 322), the first feature (54, 320) and the second feature (56, 322) do not contact each other when the first bracket (204, 304) and the second bracket (220, 318) are extended to a first length, and the first feature (54, 320) and the second feature (56, 322) contact each other -thereby setting a limit to the adjustment of the first bracket (204, 304) and the second bracket (220, 318) - when the first bracket (204, 304) and the second bracket (220, 318) are extended to a second length, a first bracket (204, 304) including a first end portion and a second end portion; a supporting frame (202, 302) connected to the first bracket (204, 304) at a position adjacent to the second end portion of the first bracket (204, 304), wherein the supporting frame (202, 302) has a first supporting section (214, 310); and a second bracket (220, 318); one of the first bracket (204, 304) and the supporting frame (202, 302) is provided with a second supporting section (206, 306), and the first supporting section (214, 310) and the second supporting section (206, 306) jointly constitute a supporting channel (207, 316) for supporting the second bracket (220, 318), wherein the supporting frame (202, 302) is a separate component connected to the first bracket (204, 304), wherein the first bracket (204, 304) has a first lateral side and a second lateral side, and the first lateral side is provided with a carrying portion (62, 216) for carrying an external object, the first supporting section (214, 310) is located on the second lateral side, and the second supporting section (206, 306) is located on the second lateral side, the carrying portion is arranged on the first lateral side of a sidewall of the first bracket, is substantially adjacent to the a lower portion of the side wall, and extends in a first direction (Dl), the carrying portion is configured to carry a bottom portion of the external object in such a way that a lateral side of the external object is configured to be pressed against and thereby supported by the first lateral side of a sidewall of the first bracket, the first supporting section and the second supporting section extend in a second direction that is different from the first direction, and wherein the sidewall (38, 208) of the first bracket (204, 304) has a first feature (54, 320), the sidewall (48, 226) of the second bracket (220, 318) has a second feature (56, 322), the first feature (54, 320) and the second feature (56, 322) do not contact each other when the first bracket (204, 304) and the second bracket (220, 318) are extended to a first length, and the first feature (54, 320) and the second feature (56, 322) contact each other -thereby setting a limit to the adjustment of the first bracket (204, 304) and the second bracket (220, 318) - when the first bracket (204, 304) and the second bracket (220, 318) are extended to a second length,