>>6867066Not sure what scale you're working with, but there's several options.
You have the train style sliding doors that you set into the 'modified plate with rail' style pieces. Those trail doors are larger pieces, but are a very thin solution.
You also have a larger variant where you can place an entire 1 stud wide wall into the rail.
https://www.bricklink.com/v2/search.page?q=modified%20plate%20with%20rail#T=A 