I live in an old house and finding a surface that is perfectly level is next to impossible so I made small tool that snaps onto the X axis rods which allows you to use the depth measurement on digital calipers to set your level according to the base of the printer by turning the Z axis rods by hand.

I made this for the Monoprice Maker Select Plus / Wanhao Duplicator i3 Plus But it should work with any printer that uses 8mm X axis rods with an rod spacing of 53mm from the top of the top rod to the bottom of the bottom rod.