There is nothing to attach the hole saw to the shaft. So when you start cutting a hole, the hole saw starts spinning off the shaft. I tried to cut a hole in the jamb and after about 5 seconds this hole saw unscrewed from the shaft and was no longer connected to the drill bit. I have several Milwaukee hole saws and they have two teeth on the shaft that go into the hole saw to keep it from twisting. A picture shows the entire saw attached with two teeth to smaller holes next to the drill bit. But there is nothing in the other picture. Is a suitable shaft supplied for attachment to the saw? The mind doesn't. Bottom line, I won't be using this hole saw again. It's too dangerous and I could do more than a few medium cuts on my arm.