I've once had a hole in the tyre big enough that I put a patch on the inside. It has held up ok, so far, but I don't know whether it would have done anyway.
Years ago, there was a small piece of fabric in a PRK with one side rubberised. This was an emergency 'get you home' patch to glue on the inside of the tyre.
Supaglue - You HAVE TO clean the split thoroughly and dry it off thoroughly. Usually in the works washroom under the hand dryer. Works OK for a few months.
Hot knife - doesn't work. Tyre rubber is vulcanised. You will only make the split bigger and then unable to be repaired.
