1. Clean crud out (if any) best you can by any means available to you, without making it worse of course. Sand/cut/file down any rough parts sticking out.
2. Marine grade 2 part epoxy (8$ home depot, k-mart wtv) - will last you like 50+ repairs.
3. Apply epoxy, have beer, wait 1-2 days. (apply epoxy with a toothpick for the cleanest job)
4. File down excess with metal file and/or 180 grit sandpaper.
5. GO RIDE