Re: TAC15/15i Weaver Rail Modification Steps
You are partly correct, in that a Sharpie Marking Pen will touch up and color the area that's been cut and make it look almost as good as the original finish, but keep in mind the original finish is a powder coating finish which is designed to stand up to moisture, scraping and all types of abuse.
The problem I've experienced with the Sharpie pens is they will rub off with very little pressure. If moisture or anything else comes in contact with them, they completely disappear. This is why I recommended the spray paint option because it applies a much more durable finish and is much cheaper than new Powder Coatings.