A clean border between beard and bottom of the neck is the best way to give a bit of corporate order to an otherwise rebellious growth of hair, a style that Chris Martin and Hugh Jackman have mastered. "The trick to getting the perfect neck line at the bottom of the beard is use the top of your adam's apple as a guide and follow your jawline outwards," says Paco O'Keefe of The Modern Man Barber Shop.
Use a beard trimmer with no shave guard to create the line and then follow up with a wet shave. The best way to check the line is with a hand held mirror, which lets you see how it will look without stretching your neck in the bathroom mirror. Keeping it clean means reinforcing the line at least twice a week. This is the hard rule for shorter beards, but once your face furniture grows out, fading and shaping from that line starts to look more conservative than a drastic line.