Loosening a bolt can be either relatively easy or difficult, depending on how tightly the bolt is attached. Over time a bolt can become stuck because rust forms on its threads or it undergoes some other form of damage. Consider several ways to loosen a bolt, starting with good old-fashioned elbow grease and ending with drilling it out after all else fails.
Clean around the bolt with a wire brush, removing as much external buildup as possible.
Try loosening the bolt with a wrench. If the bolt won't turn, try tightening it and then loosening it. The back-and-forth action might jar it loose.
Gently tap the wrench with a tool such as a a small hammer or chisel, and try loosening it with a wrench again.
Use a propane torch to heat the bolt. Heat an average-size bolt for approximately a minute--longer for larger bolts.
Allow the bolt to cool to the point where it can be touched with a finger.
Squirt (or spray) penetrating oil around the bolt. Let the oil soak in for at least an hour. The longer it soaks in, the better.
Tap the bolt again with a hammer or chisel to help loosen it, and further allow the oil to seep in. Loosen the bolt with a wrench.
Try using an extension (or pipe) on a socket wrench, which is also known as a ratchet. Loosen the bolt with a wrench.
Use a hacksaw to cut off the head of the bolt.
Drill into the bolt with an EZ Out. An EZ Out is a tool designed to extract bolts if they have become severely damaged or hopelessly stuck.
Reverse the drill, and pull the bolt out.