I was looking for a solution how i could organize/stack those cases in which different build parts (screws, nuts, resistors, transistors, sealing rings, …) are shipped in. 
Haven't found any prebuilt solution so i made my own one. 

Looks like these cases come in 3 “standard” sizes. That's what the 3 prebuilt STLs are made for. The tongue and grooves of these models intentionally fit tightly. 

You can fit the stacks to your own needs by changing parameters in the FreeCAD spreadsheet to repurpose it for whatever you want.