Here’s a question that came in via an unknown search engine: Can you replace Lionel O gauge track pins with nails?
The answer is yes, but with a caveat. The factory pins have an indentation in them that help to lock track sections together that nails don’t have, but if you find a nail whose diameter fits snugly inside the track and cut it to length, it will work. The pin’s functions are to hold track together and conduct electricity, and a cut-off nail can do that.
The main trouble you’ll run into is that indentation. Since the nail lacks a groove for the indentation, there won’t be a lot of contact between the rail and the nail, and you can expect some voltage drop at that section unless you run a set of feeder wires to both pieces of track.
So in a pinch, a nail will work, though it’s a little less than ideal.