Atlas 2540 HO/N Scale Model Railroad Track Nails are a great way to fasten model railroad track to the roadbed. Approximately 400 blackened nails can be used with Atlas HO or N Flex Track. Nails have round head and measure 1/2" long. Small Parts - keep out of reach of children. Insider Tip: Open holes in flex track ties with a small drill bit - hammering the nails through without opening the holes first can distort the track.