I have some small hardware parts, like screws, nuts and washers, that are organized into similar boxes (210x210x45mm). Although the boxes are mean to be stacked over each other, it was becoming annoying to have to lift the top boxes when I needed a part that was in a box further down. So I made this rack to allow me to just pull out the boxes I need.

The bottom section is referred to as Primary while all the other parts that can be stacked over it are referred to as Secondary. The horizontal shelf is the same for every segment. Each segment requires 4 ConnectingBlock parts, eight M3x10 counter sunk screws and four M3 nuts.