Use a Blade Guide
You will need to select the right bevel angle for your knife blade. Experts suggest selecting an angle that is approximately 20 degrees. Holding your knife at this angle throughout the sharpening process can be relatively simple for small blades, but it becomes cumbersome with a blade that is bigger than 4 inches.
To help solve this problem, you can use a blade guide. Once the guide has been attached, it will be simple to keep the proper angle elevation.
Photo courtesy Diamond Machining Technology