The VW ID.4 rear hatch has a slot that was designed to hold / store an emergency triangle kit. This triangle kit is provided in certain regions of the world, but isn't currently available everywhere. In locations where the emergency triangle isn't included, isn't available, or isn't wanted I thought it would be helpful to have a storage box that can be used in this trunk slot (in place of the triangle kit).

The trunk slot in the ID.4 can hold a box that is 430 mm x 46 mm x 28 mm. Due to Z height limitation of MK3/S+ (which is 210 mm max) , the print here needed to be split into 3 parts. While this design is very basic, it serves its purpose without being complicated. The model is printed in Vase mode with a recommended layer height of 0.3 mm using a 0.4 mm nozzle. Given that the design will be used in a car that can get hot in the summer, it's further recommended to print the parts using a higher temp material than PLA. I have used PETG for my own print and the provided 3mf project files that can be downloaded here are configured as such.

To create a complete box you will need to print out the Main Body (2x) and the Center Coupler (1x). The Main Body gets printed with a closed end bottom (and no top), but the Center Coupler is printed without a bottom or top. Since the Center Coupler has no bottom, a 4mm radial brim is used to keep the part attached to the build plate during printing.

As mentioned, attached you will find 3mf project files for use with Prusa Slicer, but STLs are also provided. You will find the SLTs are solid boxes, but (again) print them in Vase mode per guidelines above. Finally, Step files are provided if you want to modify or enhance the source design, even though geometry is extremely basic and could be recreated in no time.