While tramping through the path, Mary notices these weird little marks on the fences. No biggie… until she realizes that they match the kinds of marks Gabrielle made on the window before her demise. Wait a second… it's a code. Using it, Mary helps her posse find their way to the end of the Path.
The Gates along the Path and the Roman numerals that link them together also act like the trail of crumbs Hansel and Gretel left on their way to the wicked witch's gingerbread house. They show Mary (1) that someone made this Path on purpose, which means there may be a bigger world out there than they previously thought; and (2) that there's hope for a way out of the Forest. To Mary and her posse, the Forest is all they've ever known, so a way out of it might just be a way out of the whole Unconsecrated business. Turns out that's not the case, but it doesn't really matter—to Mary and the gang, the Roman numerals on the gates mean hope.