Ski edge tuner with angles from 86° to 89°. Works with Toko compatible files. 

Insert the nut into the slot of the model. You can either climb directly with a M5x40 screw or screw the file protection onto to screw which is a bit fiddly. 
Inspired by https://makerworld.com/en/models/460503-ski-edge-grinder#profileId-368988