Coil overs I'm assuming?? If so, what kind?
If you have two jam nuts that you would use two spanner wrenches on, you can place a brass punch on one of the teeth of the lower nut and tap it with a hammer (counter clockwise of course) to break it free. If they've been on a while lubing with WD40 first would help so you could then spin it by hand. A screw driver would work in a pinch but be careful not to blow off one of the teeth.
If you have one jam nut that has a set screw it may be a little more difficult, as some of them don't have teeth, and they are more inclined to bend / distort since they aren't a sold ring all the way around.
Either way, more info on the brand you have would help.
A big effin pair of channel lock pliers might give you some grip on it lol.