I usually use rails on almost all of my rifles so I'll put the level on it to level the rifle. Then use a combination of level on the turret and a plumb line hanging about 25 yards away to align the reticle with. Can be a little time consuming because the rings can rotate the scope slightly as you're torquing them down. I alternate tightening the screws to help alleviate that as much as possible but still usually takes some tweaking back and forth to get it level.