Putting a plug in the sidewall of a tire is a bad idea. Most automotive repair technicians that fill tire holes on a regular basis agree a sidewall plug is a risky move.
A tire plug is exactly what it sounds like. A small rubber plug is used to fill a hole in a tire. Most plugs work best on holes caused by nails and screws or other small, sharp objects.
Old school tire technicians use to plug tires by simply filling the puncture from the outside with a rubber plug. These days, tire techs use a simple procedure that involves removing the tire from the rim, stretching the rubber and placing the plug from the inside of the tire before putting it back on the rim.
Plugging a hole in the rim of a tire, or sidewall, can be very dangerous because the plugged area is under constant strain. Pressure from the entire weight of the car rests on the sidewalls and just a small amount of fluctuation in the rim can cause the plug to break loose and the tire to go flat.
