The idea is from a folding metal plastic bag holder meant to be used in kitchen, though the metal ones would be stronger, cheaper and durable, this model has what the metal one doesn't. That is being modular.
They can be put together via thick zipties or any M5 screws by using any of the braces. The braces serve as a means of making the joints bit more rigid.
Add more beams so that this plastic bag holder can stand higher and can be used for several purpose too such as foldable tray holder. You may create your own expansions such as hook or slots by taking advantage of the screw slots provided