If you’ve ever stayed at a rustic cabin or roadside motel, do you remember the sound the mattress made? It’s somewhere between a high-pitched squeak and a creak, and it didn’t take much to generate it.

These old mattresses almost always had box springs that contributed to the noise. If you’ve heard of box springs but never really knew what they were, here’s what you need to know.

What Is a Box Spring?

A box spring is a bed-sized wooden box of steel springs (or, in cheaper models, metal grid patterns) wrapped in fabric. It’s primarily used with innerspring mattresses, sandwiched between the mattress and the bed frame.

A box spring provides support, absorbs impact and improves airflow, which keeps the mattress cooler. It also raises the mattress to a comfortable height so that you’re not performing a sumo squat each time you get out of bed.

Box springs are still sold but are less common than years past, thanks to changes by the two industry leaders, Serta Simmons Bedding and Tempur-Sealy International. They started selling wood foundations about ten years ago. Box springs don’t provide the rigid support needed for many newer foam and latex beds.

Box Spring Alternatives

Most mattresses function fine when placed directly on the floor, but this restricts airflow and can lead to a buildup of dust, moisture and mold. Thus, the need for some sort of base. Until the industry-wide change a decade ago, the box spring was the most common type of mattress foundation.

“Most of today’s mattresses have tempered coils or a support layer that does not need to interact with a box spring,” says Noah Meicler, head of sales for Texas Mattress Makers in Houston. “So there are no box springs, really, any more in the bedding industry.

“The way most mattresses are created, the support comes from a tempered coil in a mattress that sits on a foundation. The mattress doesn’t need to interact with a box spring like it used to. So a box spring is a legacy term.”

Depending on the type of mattress you prefer, there are other types of supports, including:

Foundation

Made of wooden slats or a flat solid frame, foundations have no metal springs. These offer a firm surface typically for foam beds. Most foundations go with a bed frame, although some companies offer freestanding versions.

Platform bed

This is a low-profile frame with a sturdy base (wood, metal, or slatted) that holds up the mattress. No box spring required. Most have wooden legs to elevate the frame, while some include storage drawers that go to the floor. Platform beds offer an all-in-one solution but can be pricier than other options.