If you want to install a glass bed on your printer, you need to adjust the height at which the Z endstop is triggered, because the extra thickness of the glass is added to the platform. If you don't do this, you are likely to run out of adjustment length of the levelling springs and be unable to level the plate, or risk breaking the glass.
The easiest way to do this, is to add a shim to the platform at the location of the Z endstop. There are many shims available but I couldn't find any for the 2016 FlashForge Creator Pro which seems to have screws in different places than other models, so here's a remix that fits. Ready-to-use models are available in thicknesses from 2 to 6 mm (0.08 to 0.24 inch).
For those who want to make a custom shim of any thickness between 1 and 10 mm, use the Customizer button!
The shims are designed to slightly clamp themselves between the rods, but if you print them in PLA and often do prints with a hot closed chamber, they may lose their ‘springiness’ over time and become a little wiggly. This is not a problem and does not affect their effectiveness.
It is advisable to make sure the shim is perfectly flat to avoid ‘springiness’ while the Z endstop switch is being pushed, which could reduce accuracy. If the part is noticeably curved after removing it from the platform (which tends to happen a lot with ABS prints), use a hair dryer or hot water to soften it, and carefully bend it in the other direction to make it flatter.
Added Customizer to allow making shims of any thickness
Added an option to Customizer to reinforce the center of the part around the hole for the Z axis leadscrew. This allows to make thin shims that do not bend easily.