Abstract: A semi-truck trailer gooseneck assembly comprises a single curved plate extending transversely between and beyond the twin parallel longitudinal girders to form a single lower flange. The curved plate extends from the assembly supporting the floor over the fifth wheel and connecting the king pin to the trailer. The rear portion of the curved plate extends to the horizontal flat lower flanges of the twin girders extending substantially the length of the trailer. The result is a structure of increased strength and moment of inertia permitting the web depth of the gooseneck to be substantially decreased.The rear corner post comprises a two piece welded assembly wherein the major section is substantially an elongated "S" and the minor section "L" shaped. The shapes are welded together to form a hollow center portion and a pocket portion. The "L" section forms a contact for the rear door and the pocket engages the curtain to enable the curtain to be fully tightened when closed.