lightweight trays are fabricated containing a multitude of cavities in shapes for molding dobies for supporting concrete reinforcing , such as rebar . the trays are sized to fit boxes of a convenient size and weight . the trays are also designed in a way that when placed into the box they make a seal between the tray edges and the inside wall of the box . this seal allows the cavities in the tray to be filled with grout without spilling into a lower tray . the trays are also designed so that when placed into the box and turned , alternating 180 ° to each other , the lower tray provides support to the upper tray . the boxes are sealed and the dobies are allowed to cure inside the box . the size and arrangement of trays and boxes is designed to fit uniformly on a standard pallet for convenient handling , storage , and shipping .