The undercut, made popular by celebrities like Brad Pitt (and his haircut in the film Fury), flatters most men. Its trendiness has made it the go-to haircut for hipsters and finance guys alike. Walk into any fancy barbershop, and you've got a 75% chance of walking out with some form of undercut. But if you've ever been caught in line behind a particularly awkward one, you'll know what we mean when we talk of the dreaded undercut tail.

This pesky cowlick on the back of a man's head is the result of not-so-careful cutting. And because it's in the back, you might actually have one right now and not even know it's there. After all, you didn't see it in the double reflection of the barber's hand mirror—especially if it was cut wet and styled with pomade. But the more your hair grows in, the more it will appear. If you need to go to the men's room to check if you've got one, go ahead, we'll wait. Now that you've recognized the problem, how can you get it fixed? And avoid it ever happening again? Simple: We'll help you. Here's a step-by-step guide to what to tell your barber, no matter how much of a pro they are:

Don't be afraid to talk it out. Tell your barber you want a cut that grows out gracefully without a tail. They should have a firm grasp on how your hair grows and its texture before they pick up the scissors.

Be honest about your level of at-home styling skills. If you don't own any styling products, let them know that.

Ask them to give you a fade on the sides as well as in the back. The hair should get gradually longer toward the crown of your head, and it should look good whether combed straight back or parted to the side.

Related Stories for GQHair