Abstract: A reinforced box-like structure for forming a void area in a concrete formation. The structure includes a bottom panel having a plurality of spaced apart, parallel base partitions and a top panel having a plurality of spaced apart, parallel top partitions. The base partitions extend across the bottom panel and in a direction normal to the bottom panel, and the top partitions extend across the top panel and in a direction normal to the top panel. Each of the base partitions and top partitions include a plurality of double-thickness walls with a plurality of slots therein and flat top edges between the slots. The structure is assembled by superimposing the top panel over the bottom panel such that the base partitions extend transversely relative to the top partitions.

Abstract: A completely closed and reinforced box-like structure for forming a void area in a concrete formation is constructed of a flat sheet that is scored with a plurality of parallel crease lines and features a side edge reinforcing panel. The reinforcing panel has a plurality of slots thereon. A plurality of interior and end pieces are slit scored so that they may be folded to provide interior and end support units. The support units define a plurality of spaced apart partitions having a plurality of slots and flat support surfaces thereon. The structure is assembled by initially folding the side edge reinforcing panel into a position generally normal to the flat sheet to define a longitudinal rib. The support units are then attached to the longitudinal rib by registering the slots in the partitions in interlocking relationship with corresponding slots on the rib.