Rebuilding slide windows

In the process of putting in glass on the side windows last fall, I made the mistake of not taking some photos. I had to lay the project aside. Now I’m looking at the frames, which have if course become mixed. Which is right m which is left? One of the bottom parts has a “flange”  or a stiffener, on the bottom, does that face outboard or in board?  Any help appreciated!
terry