Sometimes, you grab the wrong wrench for a job. You could go back and grab the correct one, but if you're feeling especially lazy (or you just don't own the right one), Instructables user M3G points out that a little loose change can save the day.
This one's pretty self explanatory. If you're wrench is a little too big to remove a nut or bolt, fill in the gap with a variety of loose change. The coins are strong enough that you should still be able to get enough torque to loosen the bolt. Obviously, you should use the correct sized wrench or use an adjustable wrench, but when that's not an option for whatever reason, this'll work in a pinch.
Wrong Size Wrench? No Problem! [Instructables]