To use: place a hex nut into the nut trap in the tensioner and screw an M3 screw through this nut. Add an extra nut onto the end of the screw. This nut can be glued onto the end of the screw if wanted as it is just there to spread the pressure over a larger area of belt than the screw by itself would. I use this on the X-Axis of a Wanhao i3 v2, on some printers it may interfere with something and be unusable. Yes I know that I need to clean the bearing block on my i3.