Abstract: A cargo container having an improved connection between the top and side walls comprising at least one grooved metal sheet connected to and extending from each said side wall and curving to extend at least partially across the top of the container, said grooved sheet extending transverse of the longitudinal axis of the container; each sheet having a raised lip seam longitudinally and continuously formed with the length of the sheet; and a curved metal edge strip extending longitudinally of the container; said edge strip being secured to the top surface of the grooved sheet to provide a box section with the trough part of the grooved sheet to thereby strengthen the groove sheet both longitudinally with the length of the container and transverse to the width thereof. This application is a continuation in part application Ser. No. 570,949 filed Apr. 22, 1975, now abandoned.