You could use them to raise the car, but just remeber they work by pushing the springs up, and only between one set of coils, so you basically stretch the sping in the middle, so I wouldnt use em to raise a car, only lower it if at all.
They work very basically like this, you have 1 set for each spring, you put them in opposite each other on a spring, they have bolts, nuts go on first then the bits to clamp onto the sping, then nuts on top to hold it together, same with the bottom half. Its then just a matter of winding em in, or winding em out, pending if you want to go higher, or lower.
I did put something here, but it vanshied, I think
"So long and thanks for all the fish!"