Vintage developing trays?

I've aquired a couple vintage Burke & James developing trays that have a removable glass rod designed to fit down the middle of the tray. What is it there for? Was it a B&J thing?
Thanks,
Chris

I would guess it was for the seesaw development of roll film or other lengths of film and paper too long for complete immersion in the tray.

I have seen glass rods in trays that have perfectly flat bottoms - with no grooves or ridges. Without these rods, prints would stick to the bottom of the tray, and it wasn't possible to remove them without damaging an edge. With the rods, gently rocking the tray would cause the prints to lift enough to be able to grasp them with your fingers or tongs to lift them out.