When to Use "Sold by the Foot" Rubber
General purpose extrusions are your solution when:
- You're restoring a modified or custom vehicle (chopped top, vent window delete, custom fenders)
- Your specific year/make/model kit is unavailable
- You need to replace a small section of damaged weatherstripping
- You're building a Rat Rod, Street Rod, or Kit Car
Key Advantage: Universal extrusions let you buy exactly what you need—no more, no less. Simply measure your application and order by the foot.
Tools & Materials Needed
- 3M Black Weatherstrip Adhesive (GL-11)
- 7-Piece Trim & Pry Tool Set (GL-30)
- Nitrile Gloves (GL-10)
- Sharp utility knife with fresh blade
- 90-degree angle guide (for mitered corners)
- Silver marker or chalk
- Measuring tape
- Isopropyl alcohol
- Masking tape
Step 1: Select the Right Extrusion Profile
Metro Moulded Parts offers multiple extrusion profiles. Match your application:
| Profile Shape | Common Uses | What to Measure |
|---|---|---|
| D-Shape / Bulb | Trunk lids, door edges, hood-to-cowl | Gap width and depth |
| U-Channel | Glass edges, panel edges, exposed sheetmetal | Metal thickness + desired coverage |
| Round | Trunk corners, tight radius curves | Gap diameter |
| Rectangular Sponge | Door bottoms, deck lids, general sealing | Gap height and width |
How to Measure:
- Close the door, trunk, or hood
- Measure the gap between surfaces at multiple points
- Select an extrusion that is 10–15% larger than the gap (allows for compression and sealing)
Step 2: Calculate How Much You Need
- Measure the full perimeter of your installation area
- Add 10% extra for:
- Cutting mistakes
- Corner waste
- Future repairs
- Round up to the next whole foot when ordering
Example:
- Door perimeter: 132 inches (11 feet)
- Plus 10%: 145 inches
- Order: 13 feet
Step 3: Prepare the Surface
⚠️ This step is NOT optional—skipping it guarantees failure.
- Remove all old weatherstripping material
- Scrape away old adhesive residue using plastic trim tools
- Clean with isopropyl alcohol or dedicated wax/grease remover
- Allow to dry completely
- Inspect for rust—address any corrosion before installing new rubber
Step 4: Dry-Fit First
Before applying any adhesive:
- Lay out extrusion along the entire mounting surface
- Check that the profile seats properly in the channel or against the mounting surface
- Identify where corners, splices, and end points will fall
- Mark these locations with masking tape
Step 5: Handle Corners & Splices
For 90-Degree Corners (Mitered Joint)
- Use a 90-degree angle guide to mark two 45-degree cuts
- Cut through the extrusion with a sharp blade in one smooth motion
- Test-fit the corner—the two 45° cuts should meet cleanly
- Apply a small amount of adhesive to both cut surfaces
- Press together and hold for 30 seconds
Pro Tip: For sponge rubber, use super glue + activator for instant corner bonds. Apply glue to one side, activator spray to the other, press together immediately.
For Straight Splices
- Cut both ends perfectly square (90° to the length)
- Ensure cut faces are smooth with no ragged edges
- Apply adhesive to both faces
- Butt ends together firmly
- Wrap joint with masking tape until cured
Step 6: Final Installation
- Work in 12–18 inch sections
- Apply thin, even bead of adhesive to mounting channel
- Wait 3–5 minutes until tacky
- Press extrusion into position, starting from your planned starting point
- Use firm, consistent pressure—avoid stretching the rubber
- Secure with masking tape at 6-inch intervals
- Continue around entire perimeter
Step 7: Allow Break-In Period
New rubber takes time to conform.
- SUPERsoft sponge rubber is intentionally slightly oversized
- Doors and trunk lids may feel tight initially
- Allow 3–7 days of normal open/close cycles
- The rubber will compress and "memorize" its final shape
Do NOT force doors closed or trim the seal prematurely—give it time.
Special Applications
Vent Window Deletes
If you've removed factory vent windows:
- Measure the new continuous glass run from A-pillar to B-pillar
- Select window run channel extrusion (check profile matches glass thickness)
- Install as a single piece, forming corners as needed
Chopped Tops
For custom roof lines:
- Carefully template the new window openings with cardboard
- Measure all perimeters
- Select U-channel or glass run extrusion appropriate for your glass thickness
- Plan corner locations before cutting
Custom Trunk Seals
For modified trunk openings:
- Measure full perimeter at the sealing surface
- Select D-shape or bulb extrusion matching your gap
- Plan for a single splice point at bottom center (least visible)
Troubleshooting
| Problem | Likely Cause | Solution |
|---|---|---|
| Door/trunk won't close | Extrusion profile too large | Verify measurement; may need smaller profile |
| Seal doesn't compress | Profile too small for gap | Switch to larger profile |
| Corner joint separates | Insufficient adhesive or poor cut angle | Re-cut at precise 45°, re-glue |
| Seal pulls away from channel | Surface contamination or stretching during install | Remove, clean surface, reinstall without stretching |
Jan 9, 2026