I wanted to learn how to sharpen my chisels and plane blades by hand, but had the realization that it takes some practice to really learn the angles that you should sharpen a blade at. So, I figured a sacrificial piece of plastic would be a good way to do this, as I've seen something similar before. It's been a huge help for learning how to sharpen my blades and I figure it could be something that others could get a lot of use out of in training their hands to recognize the correct angles to sharpen their blades at.

This is 3D printed out of PLA because it doesn't sand very well. This means that you won't get a ton of plastic bits gunking up your stone. There are also a few magnets on top to hold the guide to the blade, which should help you keep it at the right angle. The 25* and 30* angles are for a primary and secondary bevel, which should help you keep your tools sharper for longer.