Modified garyacrowellsr's clip to hold a Pittsburg 1" Travel Machinist's Dial Indicator, item 623, as sold by Harbor Freight (http://www.harborfreight.com/1-inch-travel-machinists-dial-indicator-623.html). It's a very cheap analog device designed precisely for this purpose - measuring the distance from a mobile mount point to a bed to level it, with a "roller ball" tip so that it moves smoothly over the bed surface. The clip holds the gauge in a vertical position so that it's easy to read. The gauge mounts using the lug on the back of the dial, which is easier to assemble than force fitting the dial's shaft as the other gauge mounts on Thingiverse do. And I think that by attaching to the carriage it is more consistent with the movement of the extruders.Works very well with the new Sailfish leveling script.First, install the gauge into the clip. Before you start, make sure that the guide hole and the mounting slot are clean so that the gauge fits in place. First put the end of the probe through the guide hole, which is in the triangle at the bottom of the clip. Then put the lug back (the hoop on the back of the dial) into the slot at the top of the clip. Make sure that the probe moves freely through the guide hole, then secure the dial in place with an M4 bolt (e.g. M4-30 or longer) and an M4 nut.Don't put the clip onto the carriage yet.If you're running the latest Sailfish firmware, the "level build plate" command moves the build plate up into position, and disengages the X and Y stepper motors, allowing you to move the extruder carriage freely. If you're not running Sailfish, you can 'home axis' and then jog the carriage around the build plate using the control panel.Move the carriage to the back center of the plate, so that you have room to push the clip onto the carriage. Then clip the gauge onto the front of the Replicator's carriage. The top hooks over the fans, and the bottom then snaps under the bottom of the carriage, which may take a little force the first time, but it gets easier as the plastic flexes. This position puts the dial gauge vertical, with the dial facing the front so that it is easily readable. TAt this point, the probe should be pushed up slightly by the print bed.Use the usual thumb screws to adjust the print bed to the proper height in the center, using a piece of paper or a feeler gauge (0.001 in), then move the probe to the same location and set the 'zero' of the dial indicator. You can do this by loosening the knob at "2 o-clock" on the side of the gauge, and then rotating the bezel until the 0 is at the needle, then tighten the knob to lock the bezel into place. Then move the carriage around the print bed and adjust the print bed's height to be 'zero' on the dial. I usually start in the middle, then do the front and back center (adjusting both front or both back knobs), then the left and right center (adjusting both left or right knobs), then repeat once or twice until everything is consistently level.Then unclip the gauge, and you're ready to print.Additional notes: