I wanted to mount a dial indicator to the X-axis bars to make sure my bed was as level as I could get it. The dial indicator I got isn't anything fancy: http://www.harborfreight.com/1-inch-travel-machinists-dial-indicator-623.html Key design points: I got a 1/4 in bolt to mount the dial. Note that the dial mount allows for slop in dial indicator's mounting hole.Buy one 1/4"-20 1" bolt and matching nut. Print preferred model. If you pick unsupported, print with support. If printing model with support, after print remove support from area that goes on the X axis mount and where the dial would sit flush with the print (2 places, see bottom of print in recess). Mount dial so back is flush with where print attached to print bed. Use Z adjustment to move so dial is in a good position to measure height from print bed (metal) and follow calibration steps documented for the printer.