Can accept screwdrivers with shafts up to 11mm or flatheads up to 12mm.
The flats on the side are to permit copy/paste to join several together. Flat black to allow joining to mounting prints.
Print with circular flared-end down (touching bed).
Adjust infill as needed for heavier parts, but 3 walls and 10% infill does great for me.
The author marked this model as their own original creation.