A simple replacement rail for certain barrister bookcases. If your existing rails look like this one (albeit broken!), hopefully this will help you out.

When putting the doors back on, I found it helpful to put the rear screw in first (on both rails). This way, you have something to sort of “rest” the door on while you screw in the front screws.

I recommend printing with 3 perimeter walls, and 15-20% Gyroid infill.