the inner rail including mounting holes; a mounting member being disposed on an inner side of the inner rail adjacent to one of the mounting holes; each of the mounting holes including a vertical channel and a horizontal channel connected to each other; configured to receive a head of a bolt extending from a side of the drawer; the mounting member being a resilient strap block; a first end of the mounting member being locked to the inner side of the inner rail; a second end of the mounting member facing the horizontal channel of the mounting hole; a hollowed channel being provided between the first and the second ends of the mounting member; two resilient strap arms being formed on both longer sides of the hollowed channel; and a slope being formed on the top of the second end of the mounting member, wherein the first end of the mounting member is disposed with a central hole corresponding to a riveting hole provided on the inner rail; a positioning post being disposed on the first end of the mounting member and received within a corresponding positioning hole provided on the inner rail to pivot the mounting member relative to the horizontal channel; a pin penetrating through the central hole and the riveting hole to secure the mounting member to the inner rail; a protruding bit being disposed on the back of the second end of the mounting member corresponding to a limiting hole provided on the inner side of the inner rail; the protruding bit and the limiting hole being held against each other to pre-stress the mounting member and forcing the second end of the mounting member to correspond to the horizontal channel of the mounting hole.