Exemplary embodiments provide a sheet to form a lid to substantially close a container. The sheet comprises a rectangular base having opposing side edges, opposing end edges, an upper surface and a lower surface. At least one notch is included on each of the side edges, where the notches correspond to a protrusion on an upper surface of two side walls of the container. A portion of the lower surface of the sheet at the side edges are configured to engage with the upper surface of the two side walls of the container. A foldable flap extends outwardly from each of the two end edges. The foldable flaps are configured to fold downwardly and engage against end walls of the container. The rectangular base has a thickness of at least 0.125 inches to support weight of items placed on the upper surface of the rectangular base without collapsing.

Embodiments of this disclosure include a rigid tray container and methods and equipment for using the rigid tray container in batched process operations. In one embodiment, a mass container is sized and dimensioned to receive one or several rigid tray containers. In other embodiments, equipment is configured to lid/unlid, secure, stack, load/unload, and buffer rigid tray containers. In other embodiments, equipment is configured to stack and stage mass containers. In some embodiments, methods are provided for batch processing items.