This is a set of two Dial Gauge mounts for a 20mm T track printer like the CR-10V2 and similars.

One mount will help you to calibrate Z axis movement and the second will help you calibrate X axis movement. You can reuse the Z axis gage to calibrate the bed movement but you might have to use a clamp to attach it firmly to the frame and get the gauge level with the bed. 

I followed the advice of Teaching Tech and calibrated the movement of the axis, not a printed part. 

There is a pocket on the thicker arm for a 5mm nut. Make sure the flat part of the pocket is up so it is easy to add the nut and seal the space. 

You will need two M5 x 50mm screws and one M5 x 20mm screw to attach the gauge. You will also need three M5 nuts. It is not needed but  I add an M5 washe to keep the screw from wearing out piece.