There are several types of tire repair kits available today, and some allow the flat to be fixed while the tire is still on the vehicle. However, repairs to the sidewall should not be attempted. Damage to this area of the tire weakens its structure, and if repairs are performed improperly, the tire could fail during use.
Tire repair kits can include: foam sealant, liquid patches, rubber patches, rubber plugs and cord plugs. The type of repair needed will determine the type of tire repair kits you use. For example, if the cause of the tire damage is a large nail, then it will typically require the use of a plug-style repair kit. Or in the case of steel belt damage, the tire may need to be dismounted from the vehicle and removed from the rim in order to perform the necessary repairs.
Foam sealants are handy in emergencies. They come in aerosol-style cans, and are simply threaded onto the tire valve stem. The contents of the can empty into the tire, and the puncture is sealed as you drive. Plug-type kits contain the plug material, a lubricant to assist in inserting the plug material into the puncture and an insertion tool. The material can be either an actual plug, or a string. The plugs can either be held into place by pressure, or they become part of the tire because they are made of a material that "cures" once applied. Liquid patches require the tire to be removed from the rim, and the sealant is then applied from the inside.
Tire repair kits can be purchased at many auto supply stores, through online auto parts dealers or directly from tire repair kit manufacturers. While buying from a local reseller is convenient and expedient, better deals can often be found online, if you can afford to wait for the kit to arrive. Always follow the instructions included with the repair kit, and call tech support if necessary. Lastly, while tire repairs are fairly straightforward, remember to keep your safety in mind.