Having historically popped up across the nation under a handful of aliases—the “Citywide Special” in Philadelphia and the “Two-Step” in Texas—the beer-and-a-shot duo known as a boilermaker is hands down one of the most classic combos in existence. But there’s gotta be more to it than just a frosty beer and an ounce of whiskey, right? “Well, I would love to say that there’s a science behind the boilermaker, but for me it depends on my day,” says Keri Smith, beverage director at Doc’s Bourbon Room in Louisville. The enduring dive bar custom has become the hospitality industry’s post-shift drink of choice, following generations of boilermakers downed by factory workers following long days on the job. Smith typically finds harmony in her boilermakers by dialing up the proof on the whiskey portion, often with bottled-in-bond bottles. While the partnering pint traditionally calls for a pilsner or lager, in recent years the choice has swelled; Smith finds reliable bourbon companions in solid IPAs and sour gose beers. “I think something warm and spicy like bourbon followed by the sipper of something like a hazy IPA or a tart sour go very well together,” she says. Some prefer to drop the shot squarely into the beer and chug, but the beauty of the boilermaker is in its bare-bones versatility. “I like a shot of bourbon, neat. A nice, tall beer. Sip the bourbon. Sip the beer,” says Smith. “I know some people love to shoot the shot and sip the beer. It’s whatever works for you.”