A customer asked the other day if he should lap his rings, and how to go about it. It's a no brainer. I often use a piece of a chrome Harley handlebar that measures .9997. The first use you get out of your lapping tool or one inch bar is when your bottom ring halves are mounted on your gun and you drop the tool in. It should drop to the bottom of both rings. If it doesn't, you can move your rings accordingly, most often your rear windage screws on a Leupold type base. The front ring might require a degree or so of a turn also. It's really easily seen with your naked eye. Don't use a wrench with a towel around it. Sooner or later you will bugger a ring and it will piss you off every time you look at it. Buy a scope tool for a few bucks. They are worth their weight in gold and will last forever. Put a TINY bit of Flitz, or rouge, or lapping compound on your lapping tool, taking care NOT TO GET ANY ON ANYTHING ELSE! Remember, it's an abrasive. I cover my action with a paper towel, not cloth so I'm not tempted to reuse it. Install the top half of your rings. Not so tight that you can't move your tool back and forth, because that's what you're going to do next. Rub the tool back and forth with firm pressure up, down, sideways. Don't do it too fast to cause a lot of heat. You are simply wearing down high spots. It doesn't take a lot. Of course, if your rings have not been aligned properly in the first place you are wasting your time. CLEAN EVERYTHING LIKE YOUR LIFE DEPENDED ON IT. Including your tools. When clean, your rings will have shiny spots that were burnished down by your work. This gives your rings better contact to your scope with less chance of scratching your tube or even denting it. Most rings will benefit from this procedure, and I do it every time I install a new set.