It is the same principle as the Basic Trailer Project: https://www.thingiverse.com/thing:2516396 You can combine standard parts to build containers the way you want. There are four different corner types depending on what container type you are building, flat, tank, closed or whatever.

Scale is 1/14, same as for trailer. Should fit Tamiya but haven't tested.

You always need the same amount of Corner and Corner_mirror, because the oval hole in the corner should be longside in the upper and lower position of the container. So if you are building a standard container you need to print four Corner_3 and four Corner_3_mirror.

With Container_Corner_0 you don't need alu-profiles. You can put containercorners on a piece of wood or whatever you like.

Link to Youtube: https://youtu.be/k-VIijktbn4

Parts needed for containerframe: Alu-profile 10x10x1mm Small screws

Alu-profiles length for standard 20' and 40': H: 161mm W: 152mm L 20': 403mm L 40': 841mm