Precision Design Co. sell a couple of different style joint bars for O, S, HO and N scales. These parts are laser cut from plywood and not intended to hold track together but rather add a nice detail to your rails.
I ordered the HO scale flat, 4 bolt version, which is what would be prototypical for the era I'm modeling. The code 55 details are incredibly tiny and extremely hard to see the raised detail when on the sprue.
Once removed and glued onto my track, it was much easier to see the "bolts". Of course, the details become much more apparent as the rail size increases. Details like these are perfect for my miniature HOn30 layout since the track will be viewed close up.
As mentioned, the track I'm using is code 55 from Micro Engineering and the joint bars sit perfectly on the rail web. My locomotive was able to negotiate the rail with no problems once installed. Although incredibly small, I really do like the detail they add to my layout.