Likely, a combination of scalp and neck beard donor sites would provide the ideal sideburn for most male individuals. Scalp hair would be used at the superior aspect with neck beard hair starting anterior and superior to the tragus of the ear. If you evaluate most men with a full beard, this is the natural transition point, especially if the scalp hair is straight and the beard curls. If the scalp hair is curly, then this will be less noticeable or consequential.