They have small barbs that keep them from backing out on there own. You have to hold them in to get the pin started. They are very tight though, and difficult to remove. I was able to get them out with the machine on the ground and the front panel removed, but my hands are pretty stong and I used channel locks and a piece of rod in various configurations. If I had to do it again I'd definately tip the machine on it's side and do it from the bottom. Good luck!