This storage box product is best for file folders and other things that fit inside of the box. I found that when I put hanging files on the edges of the box that the lid did not fit snuggly over everything so either the lid needs to be made a little wider to accommodate the hanging file hooks or instructions need to be provided that hanging file folders are not recommended to be used on the edges of the box.
We have used these boxes for many many years for storing financial records-personal as well as business. They have held up in the heat of the attic and served their purpose for preservation.
Some of the boxes are not square. Look at the top corner where the cardboard is joined and glued. Check to see if the top edge lines up. Lot I purchased were as much as a half inch offset from each other. This will cause the top cover not to sit on an even flat surface. This might cause a stack to lean if heavy boxes are placed on top of each other.