OK, I finally found a picture of the frame I made. It is a bit larger than yours probably and it may be hard to see the stops because of the paint and I put LED lights in between them but maybe you get the idea.
They are used at the top, bottom and both sides of the frame to keep the glass from falling inward.
This is the front of the frame. the trim strip keeps the glass from falling outward.
Does this help you understand?
Rog