Where is the fibreglass? Is it exposed to water at all?
Hi Kathleen. Begin by drilling a tiny hole at each end of the crack. This will stop the crack from extending any further. Then wipe it down and make sure it's clean and dry. Fill the crack with a fair amount of fiberglass epoxy resin, using a plastic applicator. Let the epoxy dry for at least 24 hours.
What is fiberglass that you want to repair? Tub, wall, shower pan, exterior deck, etc?
Hi Kathleen: I think that Cindy is right on. Way to go Cindy:) Good luck