The present invention relates to boxes, particularly boxes formed from polymer materials, especially expanded polystyrene (EPS) or other expanded polymer materials. However, the invention is applicable to boxes generally, including those formed from cardboard, board, wood, metal, etc. Boxes formed from EPS or other expanded polymer materials are used in vast numbers for a huge range of purposes. For example, such boxes are used generally as transport containers, for transporting all manner of goods, including raw and processed food, plants, electrical products, chemical products, pharmaceutical products, and biological materials. Boxes formed from such materials have many advantages, including low manufacturing cost, thermal insulation properties, low density, and impact resistance. However, boxes that cannot be collapsed to a flat configuration for transportation when empty suffer from the disadvantage that the cost of their transportation (when empty) is generally significant in comparison to their manufacturing cost. While the use of boxes that can be collapsed flat for transportation when empty can solve this problem in some situations, such collapsible boxes are not suitable for all purposes nor universally adopted, wherever appropriate, in view of the fact that despite collapsible boxes having been available for many years, non-collapsible boxes are still used in vast numbers. The present invention seeks to provide a solution to the above problems and provides an improved box with sidewall having gaps to enable boxes to fit together in an overlapping configuration.