A tool I made to turn the idler knob on the Lulzbot Mini 2. Much easier than using your fingers
PRINT AT 125% SIZE.
It's made to fit almost exactly on the knob, so you may need to increase or decrease the size by one percent depending on the kind of filament you're using (watch out for elephants foot).
I printed wrenches using both PLA and Ultimaker Nylon. The PLA may grind out over time, so I'd recommend using a stronger filament if possible.