Rolling Sharpener Guide 30-37.5 degrees

I made this to allow me to easily sharpen blades from my garden shredder with my rolling knife sharpener.I designed it to use these magnets: https://www.amazon.co.uk/dp/B0B4G4DPVJ which I already had. The magnets are slightly under size and I've designed the slots to suit.There are edges on the blocks to suit 30, 32, 35 and 37.5 degree blades.