Simple stackable base plate / mount for a Raspbbery Pi (2B up to 4), so you can build your own RPi cluster. Use four M2.5 threaded inserts (e.g. https://cnckitchen.store/products/gewindeeinsatz-threaded-insert-m2-5-standard-100-stk-pcs) for mounting.

Use 25mm (1 inch) spacer with M3 threads (ideally: 25+6mm ones). 20mm might also work, but it will be a tight fit.

The 4 screw holes can also be used to screw the frame onto something else (wall, wood plate, whatever).