Although it might not seem like much, the tiny button on a car seat belt is crucial to preserving both convenience and safety. When not in use, this small plastic component, also called a stop button or retainer button, keeps the metal latch plate—the portion that slides into the buckle—from slipping too far down the strap.

In the absence of this button, the latch plate would slide all the way to the seat belt’s base, making it difficult to grab when you’re ready to fasten your seat belt. This straightforward feature saves you time and effort by keeping the latch plate in an accessible position.

The majority of seat belts have two stop buttons. While the other is placed closer to the top of the strap to make sure the latch plate doesn’t slip too far up toward the shoulder, the first is placed close to the latch plate to keep it from sliding toward the floor. When combined, these buttons maintain the seat belt in its ideal position and readiness for use.

Although these buttons are simple to replace, they may eventually wear out or break. You can install replacement buttons yourself using simple tools, and they are widely available online or at auto parts stores.