A rail mounting structure (20, 300, 400), comprising: a rail member (22, 302, 430) comprising a first mounting slot (30, 408) and a second mounting slot (32, 416); an auxiliary member (24, 308, 402) movably mounted to the rail member (22, 302, 430), the auxiliary member (24, 308, 402) comprising a first portion (36, 404) adjacent to the first mounting slot (30, 408); and a resilient member (26, 306) for providing a resilient force acting on the auxiliary member (24, 308, 402), wherein the auxiliary member (24, 308, 402) further comprises a second portion (38, 412), and the resilient force keeps the auxiliary member (24, 308, 402) at a predetermined position (P1, P3) relative to the rail member (22, 302, 430), where the first portion (36, 404) and the second portion (38, 412) of the auxiliary member (24, 308, 402) are adjacent to the first mounting slot (30, 408) and the second mounting slot (32, 416) respectively, wherein the first mounting slot (30, 408) comprises an entrance portion and a positioning portion (58, 410), the entrance portion of the first mounting slot (30, 408) extends downward from a top of the rail member (22, 302, 430) and forms an entrance, and the positioning portion (58, 410) of the first mounting slot (30, 408) extends substantially perpendicularly from a bottom of the entrance portion for a distance and the first portion (36, 404) of the auxiliary member (24, 308, 402) further comprises an extended section (40, 406) extending to a position corresponding to the positioning portion (58, 410) of the first mounting slot (30, 408), and wherein the second mounting slot (32, 416) comprises an entrance portion (60, 418) and a positioning portion (62, 420), the entrance portion (60, 418) of the second mounting slot (32, 416) extends downward from a top of the rail member (22, 302, 430) and forms an entrance, the positioning portion (62, 420) of the second mounting slot (32, 416) is located at a bottom of the entrance portion (60, 418), and the second portion (38, 412) of the auxiliary member (24, 308, 402) further comprises an extended section (42, 414) extending to a position corresponding to a position between the entrance portion (60, 418) and the positioning portion (62, 420) of the second mounting slot (32, 416). a rail member (22, 302, 430) comprising a first mounting slot (30, 408) and a second mounting slot (32, 416); an auxiliary member (24, 308, 402) movably mounted to the rail member (22, 302, 430), the auxiliary member (24, 308, 402) comprising a first portion (36, 404) adjacent to the first mounting slot (30, 408); and a resilient member (26, 306) for providing a resilient force acting on the auxiliary member (24, 308, 402), wherein the auxiliary member (24, 308, 402) further comprises a second portion (38, 412), and the resilient force keeps the auxiliary member (24, 308, 402) at a predetermined position (P1, P3) relative to the rail member (22, 302, 430), where the first portion (36, 404) and the second portion (38, 412) of the auxiliary member (24, 308, 402) are adjacent to the first mounting slot (30, 408) and the second mounting slot (32, 416) respectively, wherein the first mounting slot (30, 408) comprises an entrance portion and a positioning portion (58, 410), the entrance portion of the first mounting slot (30, 408) extends downward from a top of the rail member (22, 302, 430) and forms an entrance, and the positioning portion (58, 410) of the first mounting slot (30, 408) extends substantially perpendicularly from a bottom of the entrance portion for a distance and the first portion (36, 404) of the auxiliary member (24, 308, 402) further comprises an extended section (40, 406) extending to a position corresponding to the positioning portion (58, 410) of the first mounting slot (30, 408), and wherein the second mounting slot (32, 416) comprises an entrance portion (60, 418) and a positioning portion (62, 420), the entrance portion (60, 418) of the second mounting slot (32, 416) extends downward from a top of the rail member (22, 302, 430) and forms an entrance, the positioning portion (62, 420) of the second mounting slot (32, 416) is located at a bottom of the entrance portion (60, 418), and the second portion (38, 412) of the auxiliary member (24, 308, 402) further comprises an extended section (42, 414) extending to a position corresponding to a position between the entrance portion (60, 418) and the positioning portion (62, 420) of the second mounting slot (32, 416).