While it’s not often mentioned in conversations about the best fast food burger on the menu alongside staples like Shake Shack or In-N-Out, the White Castle slider burger still holds a special place in the stomachs of those who enjoy their bite-sized convenience. In 2014, TIME even named the slider the most influential burger of all time, with its debut in 1921 helping begin our nation’s obsession with fast-service burgers.

Peel the bun off a White Castle burger and you’ll find the square meat patty has exactly five holes. Why? Thrillist writer Wil Fulton went looking for an answer to this gastronomic mystery. It turns out that the holes serve a very functional purpose.

In 1954, a Cincinnati-based White Castle employee named Earl Howell stuffed his location’s suggestion box with a note that said the patties might cook more quickly if they were pierced. The reason? The franchise steams its burgers on the grill, and the holes allow the steam to better penetrate the stacks of patties (usually 30 burgers tall) that are piled on the grill at one time. No one has to flip the burgers, and they wind up coming out of the kitchen faster. The steam also picks up the flavor of the onion acting as a bottom layer, allowing it to spread through the stack.

Howell’s idea soon spread from Ohio to White Castle restaurants nationwide. The company facilitates the creation of the holes by puncturing a “meat log” and then slicing it and sending the patties to locations.

If you enjoy their distinctive flavor, the holes have a lot to do with it. Enjoy.

[h/t Thrillist]