I think you may be describing two different parts.
One part, called slides, sliders, hifax, runners, whatever you call them, mount on the underside of your suspension rails. These allow the track to glide easily over them and wear slowly over time.
Your tunnel protectors, or heat exchanger protectors, are on the underside of your tunnel, and yes, they protect the tunnel and heat exchangers when using studs, so if your track/studs for some reason hits the top of the tunnel they are stopped before they rip a hole in it