this is not a difficult task. set your level on a solid flat surface. the surface dosn't have to be perfectly level. put the level on the surface and note the position of the bubble inside the vial.then flip the level end for end. note the position of the bubble. your goal is to adjust the vial up or down until the bubble remains is the same spot when you flip the level end for end. this can take a while because most of those graduations on the starret bubble are set at .005 per ft. if this concept is hard to grasp take a carpenters level and put it on any fairly level surface. lets say the bubble is slightly off to the left. flip the level end for end and the bubble should still be off to the left in exactly the same spot. if it is not then your level is out of whack. the nice thing about the starrett is that you can adjust the level until its perfectly accurate. have patience you can do it .
