It requires a little practice and patience to use the spring compressor tool. Theres a lot of stored energy when a spring is compressed, so you need to be careful. On our Mustang, the old spring had already been removed. The new spring is compressed off the car. Notice how the threaded free end of the tool protrudes through the top of the shock tower. In this photo, its easy to see why you couldnt position the tool threaded end down; youd have interference with the spring perch. This means that you cant drive the tool with a socket. You have to use a wrench, bit by bit.