Originally Posted by toolboy
Especially if it's a high pressure tire. You'll find bits of stone and glass will seek out the hole in the tread. You don't want the sidewall to fail.
The sidewall shouldn't contact the road too often, but small tread cuts can be filled with super glue to prevent debris from getting in. I forgot to mention to coat the inside of the tire and the patch separately with rubber cement and let each dry before attaching the patch.