This part attaches to the screws that also hold the 40mm hotend fan. For Anycubic Mega, the original screws can be used, for other Printers longer M3 screws may be required. 

The part is shaped such that airflow through the fan is still possible. It is small enough to remain on the printer at all times and does not interfere with the printing operation. 

To be used with dovetail slot tools. Slot them in and push down with roughly the same force you want the tool to be exposed to in the event of a tool crash in Z-direction. The tool is held precisely in the fit and will dislodge itself if the absolute force with which it was inserted is exceeded in an upward direction.