So, it's important to not shave your neck when you are in early stages of your beard, even if a designer stubble stage.
25+ Faded Beard Neckline. To pull off an awesome neckline fade, you're going to need a trimmer with multiple guards or settings. A beard is not of use until one can maintain it well.
How To Trim A Beard Neckline The Right Way from i1.wp.com
Let it grow and trim it back to normal. Beards demand a good deal of attention and maintenance to get the maximum benefit from it. Go one or two settings shorter on the clippers.
Bad beard neckline to avoid.
Hard line under the chin. Learning how to fade your beard neckline properly is one of the harder parts of the shaving routine. A beard is not of use until one can maintain it well. It should stop at the angle where your neck meets the underside of your jaw below your chin.