3-in-1 DIY Knife Sharpening System Jig

[Mazay]

If you're not reprofiling an edge, the best way to set the angle is to draw on the bevel with a sharpie, then find the correct angle using light test strokes that grind fully across the edge bevel by observing the ink taken off.

This is a good tip - I use a felt-tip pen when sharpening a chisel and a scissor (I prefer to sharpen knives on the protractor)