I'm trying to sharpen a drop-point knife (benchmade griptilian). I use a work sharp guided sharpening system with angle guides and am trying to follow the 20 degrees per side recommendation. All the manuals and instructions suggest I rest the blade on the guide, but I don't understand whether I rest the bevel or the "body"?
The angle is measured from an imaginary line that goes through the center of the blade from the spine to the edge. It is assumed that the top part of the blade (in red), is parallel to that line. Therefore it would be the red part of the blade that should be flush to the guide. A pro tip to check if you're on the right angle is to use a permanent marker and color in the fine edge. It will result in a thin black line on your secondary bevel (assuming it has one, most do) which is the very edge of your blade that you're trying to sharpen. Then when you sharpen, you'll immediately see what part of the blade is in contact with your sharpener and if you're at the correct angle.
If look at the demo videos or read the manual on the webpage for work sharp sharpeners.
It seems pretty clear from the manual alone, that it should be spine of the blade against the angle guide, with the cutting edge down towards the grinding part of the tool. This will allow the cutting edge to be at the correct angle relative to the grinding part of the tool.