Also, once you've soaked them in some kind of penetrating
oil and begin to try to get them off,once you hit one and it starts moving,once you get about 1/2 turn on it, then knock it back to tighten it,then knock it back to loosen it ad go 1/2 turn at a time,tighten/loosen:tighten/loosen till it comes off......
Just extra insurance against galling the threads....you only need to do this on something that has not been loosened for years......
David