I removed all four corner screws from my shower door in order to adjust sag. Unfortunately whatever is inside the door pulled away from the holes and now I can no longer reinstall the screws that I removed. Anyway that I can fix this?
Inside the door frame is a tube like opening that runs the length of the frame. It is an integral part of the frame and is formed when the metal is extruded through a die.
The opening usually gets broken or is forced wider when the screw is turned to tight. Also corrosion occurs over time.
You can try this first: get a screw of the same diameter as the original, but slightly longer. You may be able to reach a sound section of the adjoining frame.
If not carefully separate the two miters until you can see an attachment point. This is not something that is easy and can be dangerous.
All you can do at this point is disassemble the door and line up the missing pieces. There will be some rubber gaskets around the glass that will have to be put back in place. Work on one corner at a time, secure it with the screw and then go to the next corner. when the four corners re assembled, tighten all four screws.