Abstract: The invention relates to means for and methods of forming containers. The means comprises one or more pieces of corrugated cardboard adapted to be inserted into standard bags usually provided by stores for carrying purchased commodities. A cardboard piece is bent along scored lines to a form wherein it will fit within the bag to shape the latter widthwise, the excess upper portion of the bag being folded into the bag and over the cardboard piece to form a container. Another corrugated cardboard piece, if a different width than the first mentioned piece, is bent along score lines to a form wherein it will fit within another grocery bag to shape the latter endwise, the excess upper portion of the bag being folded into the bag and over the cardboard piece to form a container. One of the containers may be inserted into the other to form a dust-proof storage box or a shipping container.