So I am almost done with my build and have a question about bed leveling. Since all four corners have springs none of them are fixed, and if I choose one (say the back right side) and adjust the other corners using a piece of paper and the extruder head I still am not leveling off of a fixed reference because one z rod could have the nut a little higher or lower than the other so that when I move the extruder to the back left corner it could be going up or down. Should I use an actual level to level the bed and then adjust my left and right z rods to ensure that the x axis is level relative to the bed? Seems more like we are just assumeing the x axis is level and then we level the bed to it?