So yesterday (and today) I was working on putting lower parts kits in some stripped lowers, something I have done many many times before. I have a well stocked and set up bench with all the tools and gadgets one needs for a quick and easy AR15 build. Toward the end of the assembly I realized I had still not installed the forward pivot pin, which also means installing a spring and detent. Now I am smart enough to know that when works with things that can fly under under tension, one wears safety glasses. But apparently I was not smart enough to remember where I put my pivot pin installation tool. Oh well, those are just for convenience anyway. Or so I thought until that little detent popped out when I was sliding in the pivot pin and pushing out a plastic dowel. I heard at least one and perhaps two ricochet, none of which involved bouncing off my safety glasses. I looked all around and of course could not find it that tiny little silver thing on a gray floor (in a room that is entirely too messy). If I was not well prepared that would be the end of things for me until I could acquire another detent. Instead I went to my "Oops Kit" and pulled out a spare detent and finished the build. And let's not pretend this is the first time that Oops Kit came in handy. A good reminder to me that having spare parts is not just a luxury. If the supply chain suddenly comes to a close, it will be a necessity.