What Kind of Fasteners Are in Cars?

So many different parts and pieces go into cars, it would take an entire book to list them all. For now, though, we’re going to take a closer look at the fasteners in cars that hold it all together.

Screws

Screws are threaded lengths of metal designed to hold two or more things together, and you will find them in nearly every part of your car. The main difference between screws and bolts is that you don’t always need existing threads to install screws — self-tapping screws can create a threaded hole in plastic, metal or wood.

Screws generally have two different heads — flathead or Phillips head. Flathead screws have a single slot, where Phillips-head screws have an X on top that provides extra grip for the screwdriver to keep it from stripping when placing or removing a screw.

Bolts

Unlike screws, bolts need a threaded location for appropriate placement — and you need to have a bolt with the proper thread pitch and thread count to fit correctly without damaging the existing threads.

Bolts usually have a hex-head, which requires a correctly sized socket or box wrench to remove. It’s important to get the right size socket or wrench — being off by just a little bit will cause you to strip the head off the bolt and make it impossible to remove. Some tools make it possible to remove stripped bolts, but you will need to replace the bolt before you can put your car back together.

Nuts

If your bolts don’t have a threaded slot to fit into, they’ll have a nut on the end to hold them in place. The nuts will have to match the thread pitch and thread count of your bolts. Nuts come in two varieties — nylon or steel. Nylon nuts often pair with nylon bolts, but they can also go with steel bolts in non-load-bearing applications.

Steel nuts can have several different finishes, depending on the applications. In areas where the nuts might encounter water, corrosion-resistant zinc or aluminum finishes might be common.

Grommets

Grommets are probably the most annoying fastener in your car. They’re usually plastic, hold together things like fabric and plastic body parts — and tend to break every single time you try to remove them.

You won’t find plastic grommets in load-bearing applications. Instead, they secure things like your car’s headliner, the liner of your trunk or the plastic covers in your wheel wells. Thankfully, they’re easy to get your hands on if they do break, so don’t worry too much about a broken grommet or two — just replace them, and you’re good to go.

Washers

While washers aren’t officially a fastener, they are a vital part that helps these fasteners do their job. Washers can lock nuts or bolts into place, to widen the head of a bolt or screw so it can fit into a larger hole or to give the finished product a clean look.

This list only scratches the surface of the fasteners in cars, but it’s an excellent place to get started. You don’t want to try to put a screw in a bolt hole or get your washers mixed up with your grommets when you’re working on your car.