Rusted or extremely tight bolts can be impossible to get out on their own. To remove them, you may need a little extra help. There are several ways you can remove a stubborn bolt. Through trial and error, you'll learn which works best for you. Here are some ideas to try the next time you have a stuck bolt.
Pour penetrating oil, found at most hardware stores, onto the bolt. Liberally soak it and try to get it into the shafts, the twisted part of the bolt, if possible. Let the penetrating oil sit for several hours.
Use a ball-peen hammer and a chisel to chip away at the bolt. Any rust holding the bolt in place should chip off.
Pour Diet Coke onto the bolt. This can be used instead of penetrating oil or if the penetrating oil won't work. Scrub the bolt with a stiff material such as stainless steel wool. Hydrogen peroxide can also be used in the same way. Wait a few hours before scrubbing it off.
For stubborn bolts, use a propane torch to heat the bolt, and pour cold water over it after it has turned red from the heat. This will help the bolt to crack and loosen, allowing it to be taken out. Do not use this method if you have poured any liquids over the bolt, such as penetrating oil, which can be extremely flammable.