These are very small containers that are not designed to carry much weight. I wasn't sure what to expect, but they worked well for my range of PC parts: CPUs, memory, screws, small PC tools, etc. I wouldn't recommend them for attaching real screws or roofing screws. The back panel is not strong enough to withstand a large load. It is made of lightweight plastic which is why I only gave the product 4 stars. The boxes are strong enough, even small ones, to carry a heavier load. I will most likely be putting these containers on the shelves of my closet, so will buy more in the future as needed.