It's just a paper test to see whether a scope is tracking properly or not. It'll also let you know if your crosshairs are level. Any scope that is going to be dialed needs to be put through one. Although most won't and most would be shocked what they found if they did do one. You'd see a lot of instances of scopes not doing what you tell them to do. Too many folks try to make scopes a viewing device when they're forgetting it's an aiming device first and foremost. I don't care how good of glass a scope has if it doesn't do what I tell it to do when I tell it to.

Sent leaning against a big oak in knee deep water