Requires an M2 or M2.5 screw. Thread rolling screws are better than machine screws. This design does cover up the back of the header pins on the long side. 

I designed the FLIP_C3, available at vdbx.io, with the intention of replacing my existing microcontrollers running ESPHome. Many of those are in DIN rail enclosures so I designed this DIN rail adapter for the FLIP_C3