Matching the rail to the action, and fixing it in place. (https://ysterhout.net/docs/basefix/basefix.htm)
In addition to the above, I had to replace some of the rail screws on both rails, some of the screws were engaging two or three threads before the bedding, so I replaced them with longer ones to use all but the last thread in the action holes.
I have a rifle where in the past was necessary to attach the rail to the action with 6mm screws. After this exercise, I realise I could have just used 4mm screws on that one, and bonded it to the action for the same result.