The undercut ... the haircut, on the Irish lads in "Peaky Blinders" and the Jersey guys in "Boardwalk Empire," both cable series set in the 1920s. Somehow this cut looks retro yet modern, tough ...

If you're opting for a more classic or undercut pixie (where the hair is cut shorter on the sides and then longer on the top), the haircut itself will be of prime importance, while modern ...