Answer to "What kind of bit could I use"This type of screw seems to be common in power strips in (some parts of) Europe. Its head is only about 5mm in diameter at its thickest, and they tend to be seated quite deeply within the power strips, making extraction difficult. It also seems to be a genuine “security” screw because it really is difficult to find a driver for it. The closest match in dimensions seems to be the “#6” tri-groove socket that’s sold in the US, but on the pictures it appears too thick to fit the deep screw holes in these power strips. I’d managed to drive it with snake-eyes but it wasn’t efficient and it definitely won’t work for fastening it back into place.