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Our Simple Guide to Weatherstripping Terms

Have you ever been shopping for weatherstripping and looked at some of the names of the parts and thought to yourself “What in the world?”. Yeah, we know. There can be some pretty odd names for this stuff.

Some of our parts names are self-explanatory like ‘Trunk Weatherstrip’ or ‘Windshield Gasket’ but there are plenty of names that are not. To help translate some of these crazy terms we put together this handy guide that explains it all.

So pull up our website at and search for parts for your vehicle or grab your custom catalog (you can request one here) and use this information to guide you through the process.

Let’s start with some basic weatherstripping terms:

Dense extrusion is made of a solid rubber. Its flexible to bend around a curve but doesn’t really compress at all. A windshield gasket will almost always be made with a dense extrusion.

Sponge extrusion is just like that- a sponge. Our sponge extrusions are closed cell sponge rubber (meaning they don’t absorb anything) but can withstand pressure for long periods of time without losing its shape. It’s soft and squishy and easily compressed. Many door and trunk weatherstrips are made with sponge extrusion.

Clinch seal– A sponge rubber seal that’s attached to a flexible, dense-covered, metal core with rubber fingers inside the channel. These are designed to be pushed on to a pinchweld. The rubber fingers help prevent the seal from slipping off, while the metal core helps grab onto the lip of whatever you’re sealing. Most often a clinch seal also has a bulb attached but can also have other appendages. These seals became popular in the mid-70’s and are used on most modern vehicles to seal the doors and trunk.

Vulcanized– When we use this term it means that two or more pieces of rubber are molded together. For instance, when we make a windshield gasket it’s a complete circle of rubber made from an extrusion. The two ends of rubber are put into a mold with some additional rubber, heated up and vulcanized, or molded together, making them one unit that won’t separate. We do not glue or join our rubber ends together any other way.

Flocked– If something is flocked it has a velvety coating. For weatherstripping that often means that part is made soft and meant for glass to slide against it.

A bulb seal has an open, rounded or teardrop shaped bulb on them made of sponge rubber and are typically used on doors and trunks. They are made of the soft sponge rubber so that they compress yet hold their shape, creating a watertight seal.

Up next- individual part names:

Beltline weatherstripping– This part has a ton of different nicknames like window fuzzies, anti-rattle, windowfelts, cat whiskers, window scrapers, window sweeps, etc.

There is an inner beltline (sealing between the door panel and the inside of the window) and an outer beltline (sealing between the door and the outside of the window).

These parts mount to the top of the door where the window rolls down into the door and they ‘sweep’ the window as it rolls up and down. They’re what you rest your arm on when you’re riding with the windows down.

Beltline weatherstripping prevents window rattles making for a nice, quiet ride. It also prevents water and debris from getting inside your door causing dreaded rust.

Roof rail weatherstrip– This important weatherstrip comes on all hard tops and convertibles. There are two types- the hardtop roof rail and the convertible roof rail.

The hardtop roof rail weatherstrip is mounted along the roofline of the vehicle and seals between the body and the top of the window when the door is shut and window rolled up all the way. This is super important to eliminate leaks, rattles and wind noise while driving down the road.

The convertible roof rail weatherstrip is a series of molded parts that mount to each section of the convertible top and seal between the convertible top and the top of the window when the door of the vehicle is shut and the window is rolled all the way up. If you’ve ever owned one, you know how important weatherstripping for a convertible top can be.

With the Convertible roof rail weatherstrip often comes the header bow (or front header bow). The Header Bow runs across the top of the windshield and seals between the convertible top and the windshield frame when the top is closed.

Run channel– Run channel is a metal or rubber U-shaped weatherstrip. There are 2 types of run channel- flexible and rigid.

Flexible run channel runs up and over the window in the window frame and seals the window when it’s rolled all the way up. It’s called flexible because it has a metal spine but it’s made to bend around the curve of the window. Flexible run channel is normally held in by tension but you can use a clip or two to attach it if needed.

Rigid run channel runs vertically in the door and guides the window as it goes up and down. Typically, only found on the channel opposite a vent window. There are sometimes two pieces of rigid run channel in a door- one that’s above the beltline and one that’s down inside the door below the beltline. Rigid run channel just pushes into the metal channel already on the vehicle- no clips or adhesive required.

Additionally, mohair liner is sometimes glued into a metal channel for use as run channel. Mohair liner is a soft, thin fabric with a thin rubber backing and is used to prevent glass from sliding against metal

In the 1960’s auto manufacturers started using rubber run channel in place of the metal, felt lined channels. These can take many different shapes for different applications and typically just push into the channel already on your vehicle- no adhesive or clips required.

Sash channel- A metal U shaped channel that’s installed horizontally inside the door and supports the window glass from underneath. This is the channel that’s attached to the window regulator.

A Sash channel filler is a piece of rubber that’s mounted to the bottom of the glass to protect it from the metal sash channel and to prevent rattles. This can be a molded part, specific to a certain vehicle or just a thin strip of rubber cut to length and pushed into the channel.

Lock pillar filler– This part seals the gap at the bottom of the rear side (quarter) window. Usually only found on hardtop and convertible models where there is no B-pillar. Sometimes referred to as “U-jambs” they’re often shaped like a “U”. Without this part water and debris could collect inside the body leading to rust. Ain’t nobody got time for that.

Hood to cowl– This weatherstrip seals between the top of the firewall and the back edge of the hood. This weatherstrip seals snugly to prevent fumes from entering the cab of the vehicle. This piece typically runs the width of the car, and many vehicles require special clips for installation.

Division post seal- Everyone has heard of vent window weatherstrips but the division post seal doesn’t always get called out by name. For those vent windows that have a two-piece seal, the division post is the straight piece that mounts to the vertical post on the vent window. The main vent window weatherstrip installs into the frame, sealing the other sides of the triangle. A division post seal often has attaching tabs that correspond to holes in the vent window frame. If yours doesn’t have holes, you’d simply glue it in.

Divider bar seal– The piece of rubber that divides two pieces of glass in a two or three-piece windshield or rear window gasket. Here at Steele it comes molded into the gasket or sold as a separate piece (depending on the individual application and how it was originally made).

Hinge pillar– Attaches to the body and seals between the A-pillar post and the front section of the door or vent window frame when the door is closed. Typically, only found on convertible models. This is like the A-post section of a hardtop roof rail but then ends due to, you know, no roof.

Side window leading edge– This part is specifically for hard tops and convertibles. It is a strip of rubber that attaches to the vertical edge of the rear side windows and seals between the front and rear windows when both windows are fully raised and the door is shut.

Splash apron seals– Pieces of masticated rubber attached inside a fender well to prevent debris from entering the engine compartments. Splash shields are usually partial cover pieces and as such, a vehicle may be fitted with only one splash shield, or multiple ones that cover different sections of the wheel well. These are attached to the vehicle using screws, bolts or clips.

A-arm dust shields function the same as splash apron seals but are custom-shaped to wrap over “A” shaped control arms without posing an impediment to their motion.

Locking strip– A rubber or mylar strip that accompanies many windshield and read window gaskets. It’s designed to fit into a receiving slot in the gasket to tighten it up and create a seal. The gasket is placed on the vehicle first, then the glass is placed in the gasket. Then you can install the locking strip into the slot in the rubber and it expands the rubber creating a seal all the way around the glass.

Bumper bullets– Conical shaped bumper guards on the front bumper/grille assemblies of some post war American cars in the 1950’s.

Bumper guard– A rubber piece mounted to the bumper to protect it from minor dents and scratches.

Gravel shield/stone deflector– Molded rubber piece or extrusion mounted onto the vehicle to prevent damage to the vehicle from stones deflected by the front wheels of the car.

Body mounting pads– Thick, heavy-duty pieces of rubber between the chassis and body of a vehicle. They prevent metal on metal rubbing and make it easier on the frame that supports the vehicle. Also often called biscuits.

Bumper grommet– A rubber grommet is made specifically for cars where the arms that hold the bumper go through the fender. The grommet fills the hole preventing road debris from entering the fender and gives it a decorative look.

Other miscellaneous terms:

Revulcanization– Here at Steele revulcanization is the process of stripping the old, dried out and/or damaged rubber off a metal core and molding new rubber onto it, making it like a brand-new piece. We offer revulcanization services for parts like motor mounts, transmission mounts, harmonic balancers, accelerator pedal pads, vibration dampers, etc. on specific vehicles. See our website for more details.

Masticated rubber– Strong rubber sheet containing random milled cotton cord reinforcement for making splash aprons, etc.

We hope this clears up the mystery behind some of these weird names and made you feel more comfortable with and knowledgeable about the parts on your classic. A lot of these names come from the original parts books and what the Engineers who designed them gave as the nomenclature.

How’d we do- did we miss anything? Or do you have a different name for one of these parts? Comment and let us know! With more than 60 years in the business, we’re the weatherstripping experts and our passion is helping you restore the car of your dreams.

Steele not only has all the products you need but all the knowledge you need to get the job done right, too. If you have questions about Rubber Parts or Weatherstripping on your Classic Car, Truck, Hot Rod or even your boat, trailer or RV, feel free to reach out to us! You can call us at 800-650-4482, contact us through our website or comment on this post and we’ll get you answers as quickly as possible. Check out our YouTube channel for our full library of how-to/installation videos.