The first plugs that I recall was about 50 years ago. I was hanging out at the gas station one day and this guy drives up. Ask the owner if he plugged flat tires, he said no, the sales guy say's can I show you something? As they walked out to his car the guy took out a ice pick and stabbed his front tire in the sidewall. The tire looked like a chia pet it had so many plugs in it. Anyway the guy took a plug out of his kit and plugged the leak, then asked , you want to buy a kit? The owner of the station said yes. I have a plug kit that I take everywhere for emergency's, but when possible I use the plug patch system where the tire has to be removed from the rim, proper clean and prep for the patch then the plug is pulled through from the inside of the tire to seat the patch correctly. Never had a tire fail from this procedure. I wouldn't recommend doing a sidewall though.