While fixing the stair door today, I found that the door closer had been (inadequately) fastened to the frame using a type of screw that I've never seen before.
The screw is a straight cylinder, with a fairly low profile thread (bit more than a bolt, but less than a wood screw thread); it has a partly smooth shank; but unusually, part of the tip is also unthreaded, and the tip is formed in a precise sharp conical point. The unthreaded tip portion comprises the point and about 1.5mm of cylindrical shank before the point. It has a Pozidrive head, and is made of brass, if that's relevant.
What is it? I haven't even managed to google up any pictures of such a screw.