If you are talking about what I think you're talking about, those are gauging ties. It looks like an oversized Arrow track-tie, and it has an adjustable bolt on either end. It's attached to the track and the carpenters can adjust the bolts to fine-tune the track width in those areas.
On The Beast at Kings Island, the same thing is accomplished using long bolts that extend all the way from one side of the track to the other. That won't work on Mean Streak because the brake fins on the trains hang down too low; the center of the track has to be kept clear. So they use the steel gauging ties instead.
--Dave Althoff, Jr.