Originally Posted by spaghettiroad
so sheet metal or whatever used on the backside is removed and replaced with fiberglass to bond once mold is in place?
Yes....the NEW GALVANIZED SHEET METAL (not what ever) is the mold and is removed after the fiberglass work is done and you are done except for the finishing. The repair is made. It is the "mold" or backer for the new glass then is removed after the glass cures. Then you saw or trim to final shape. You can get a small galvanized piece of metal at any lumber yard or home depot in the roofing section. Ask for a "tin shingle"
Fiberglass Dave. I have a thread on fiberglass repair on this forum that may or may not help you.