Originally Posted by capequahog
the bolt that holds the lawnmower blade on is frozen won't budge...
First things first.
Disconnect the plug high-tension wire.
Wedge the blade against the case with a 2x4 block or something similar.
You need to know which direction the nut tightens and loosens.
If unsure, look at the direction the blade turns. (Note: it'll turn in the direction of the cutting edges.)
Facing the blade with the nut closest to you, loosen the nut by turning it in the same direction that the blade turns.
Use the correct size socket. And unless you have arms like an orangatan, put a cheater on the ratchet.
Or you can do as suggested and use an impact wrench. Either electrical or mechanical. Either one should work.