a keeper 44 consisting of a segment of an angle is welded to the side rail 28 with the panel in stored position the member 42 lies behind the keeper and serves to hold the free end of the panel against the container wall pin 42 is placed behind the keeper by lifting the free end of the panel in the direction indicated in fig1 the slight degree of rotation of the panel necessary for this action is permitted and limited by the elongated configuration of sleeve 36 at the upper pivot 24 the rotation which occurs at the universal pivot 26 is permitted by the normal clearance between the pins and their holes pin 42 also serves as a support for the free end of the panel during rotation through arc c fig2 in this position the pin 42 abuts against stop 47 welded to the top of rail 30 fig1 the inclined surface 43 on pin 42 facilitates the turning of the pin against the rail 30 under the weight of the panel pin 42 has a third function when the panel is in horizontal operative position it lies behind stop 47 and prevents the panel from slipping off the rail 30 should the panel flex due to the imposition of heavy loads a similar pin 48 at the upper left hand corner of the panel may be provided to insure maintaining the panel in horizontal position pin 48 cooperates with stop 49 fig1 secured to rail 30 it will be understood that like stops are provided along the rails for the cooperating pins on each panel the panel is moved.