Scope Laping

What does scope laping do and when does one need to lap his scopes?

If you are asking what I think you are asking, you lap the scope rings, not the actual scope.

It trues the rings to each other on the receiver, which keeps the rings from exerting any odd pressure on the scope.

This guy's site has pictures of the tool and the process. You can see in the last few pictures how much he "took off" of the rings to even them up.

http://www.centerfirecentral.com/lapping.html