Believe me, it works, I've repaired a dozen or so saws with it. Attaching that strong spring is a nightmare without it. I once used a cable and pulled it on, but that will not work on many saws because the case blocks the cable. One of my buddies made his by milling a 6" length of small angle iron. But, he likes mine better.Holy cow, I have one of those that I got in a box of random chainsaw tools, and I didn't even know what it was for.