Abstract: A cardboard retaining structure defined by a peripheral strip joined at the ends to form a continuous loop and creased to form fold lines thereacross. The fold lines are spaced to define substantially equal front and rear panels in the strip separated by substantially equal lateral panels. The loop therefore may be collapsed into a folded planar structure one or more separator panels extend between the front and rear panels and the front panel is provided with a notched flap to engage the edge of the separator panel in an orthogonal alignment therewith.