Everybody with a kitchen has a decent knife, a cutting board or two, and some mixing bowls. In our column Surprisingly Useful, we’re going beyond these basics and talking to chefs, authors, and food writers about the unexpected kitchen tools they can’t live without.

Jon Shook makes a lot of fried chicken sandwiches. His Los Angeles restaurant Son of a Gun serves about 60-75 fried chicken sandwiches per day, in fact. Chatting with him recently, we learned that one of the secrets behind the sandwich is in a clever little machine that’s often found in diner kitchens—designed with the sole purpose of efficiently and evenly buttering bread.

What is a butter wheel?
A butter wheel is basically a pan with a hamster wheel that sits inside of it, and it’s used for buttering bread and buns. Typically it’s found at fast food restaurants. We just had it out last night at an event we had and so many people were like “what is that?”

How did you find out about butter wheels?
A lot of this stuff I saw along the road cooking at different restaurants. And more in high school, when I was working at Mom-and-Pop restaurants.

Do you use it at home?
Never. I cook super simple at my house. Very basic. Usually when I’m cooking, I use one tenth of the equipment that I have at my house. I use a lot of sauté pans, and I barbecue a lot.

Have you ever used it for anything other than butter?
Sometimes I’ll make garlic bread, or put spices in there. But in general, pretty much all I’ve used it for is buttering bread.

How does it work?
Basically it has melted fat in the bottom of it. As you run something along the wheel, the wheel has little microscopic holes, so as it spins, it kind of pulls the fat up onto whatever it is you’re running across it. It helps distribute the fat content directly across the entire piece of bread, which then helps to get a more perfect toast. If you don’t butter it all the way across, you don’t get good toast.