If you look carefully at the photo above, you can see that the person sitting in position to row on the Concept 2 rowing machine is sitting on a seat which is riding on a rail. The photo below this paragraph gives a less obstructed view of that rail, from the viewpoint of a person sitting on the seat, with the seat all the way back to the end of the rail.
So now you know, in case you didn’t already, what is being referenced in the title with the word, “rail”.
Today’s rowing on the rail session was a half marathon done in the company of a rower in Denmark and a Rower in Netherlands or perhaps Spain. (He has rowed from both locations and I didn’t ask him which country he was in today).
Happy rail rolling to you.