How to Loosen Nuts and Bolts
Try Penetrating Oil
Spray the nut with penetrating oil and let the oil sit for 10 to 15 minutes to penetrate the threads of the bolt. Then use a wrench to try and loosen the nut.
Use Two Hammers
Hold a hammer against one side of the nut, and hit the other side with a second hammer. That might loosen the nut so that a wrench can remove it.
Try a Hacksaw
If the nut is badly rusted, pour hydrogen peroxide on it to dissolve the rust. If that doesn't work, saw through one side of the nut with a hacksaw. Then loosen the nut by twisting it with an adjustable wrench.
Cut a Groove
If the head of the bolt is buried in your work piece, use a hacksaw to cut a groove in the top of the bolt. Stick the end of a screwdriver into the groove to hold the bolt steady while you loosen the nut.
Try a Nut-Splitter
A nut-splitter is a handy tool to remove nuts. It has a chisel inside its head that is screwed into the nut to pop it off.