FlashForge Creator Dual Extruder Shim for Glass bed add on.

thingiverse

This is a shim for the FF Creator Dual extruder printer. The purpose of this is if you add a glass plate to your build the printer will need to know to detect the change in depth where the sensor is. The shim triggers the sensor so that the hot ends do not break your glass or scratch it (break it more likely). This one is 3.1mm width, yours may be different. Always make sure to tighten down your bed so it gives you more clearance when you start to level it. Please if you found this part useful - consider donating a dollar or two.