What is BackBone Reinforcing Mesh?
KBS BackBone Reinforcing Mesh is a thin, nonwoven C-glass fiberglass cloth that embeds into wet RustSeal to bridge pinholes, small gaps and weakened areas in metal, wood or fiberglass. Each envelope holds one 36 x 36 inch sheet (1 square yard), 0.010 inch thick, that cuts to any shape with scissors or a razor blade.
36 x 36 in
One Sheet (1 sq. yd.)
0.010 in
Thickness (0.26 mm)
0.77 oz
Weight per sq. yd.
C-Glass
Random Nonwoven Fiber
BackBone is a thin, pliable reinforcing fiberglass mesh that lays flat to form an invisible patch with unbeatable strength and holding power. The soft, flexible cloth is easy to use: no bunching, no bulging and no stiff loose hairs to ruin your finish.
Use BackBone with RustSeal or NuMetal Epoxy Putty to repair holes and bridge gaps in metal, wood or fiberglass, and with Gold Standard Tank Sealer to reinforce pinholes and weld seams on the outside of a fuel tank. The mesh embeds into the coating instead of fiberglass resin, so the repair is sealed against rust as it is reinforced.
BackBone Reinforcing Mesh repairs pinholes, weakened areas and small gaps that are too large for RustSeal alone to plug. KBS BackBone applies to metal, wood and fiberglass with RustSeal, and reinforces holes up to 3 inches across when layered with NuMetal Epoxy Putty on non-structural panels.
- Pinholes: BackBone embedded in a thin coat of RustSeal closes pinholes left after rust removal.
- Weakened, thin metal: The mesh adds a layer of reinforcement over metal that rust has thinned but not holed through.
- Small gaps and holes: BackBone bridges gaps and holes, adding a layer of additional security to the repair.
- Floor pans and trunk pans: The mesh molds to the shape of the pan and is part of the KBS Trunk and Floorpan Repair Kit.
- Rocker panels and cab corners: Mesh and NuMetal rebuild non-structural rust holes before the area is coated.
- Fuel tank exteriors: Embedded in a thin exterior layer of Gold Standard Tank Sealer over pinholes and weld seams.
- Wood: BackBone applies to wood with RustSeal or NuMetal to repair holes and bridge gaps.
- Fiberglass: The mesh reinforces fiberglass repairs with RustSeal or NuMetal.
BackBone is a random nonwoven C-glass mesh only 0.010 inch thick, so the cloth lays flat in wet RustSeal instead of bunching or leaving stiff fibers standing above the finish. KBS BackBone weighs 0.77 oz per square yard, carries a resin absorption rating of 9.4 oz per square yard, and forms an invisible patch with strong holding power.
- Lays flat: No bunching, bulging or stiff loose hairs to ruin your finish, so the patch disappears under the topcoat.
- Soft and pliable: The thin cloth molds into curves and pan shapes with a brush.
- Strength and holding power: A soft, thin cloth with amazing strength and holding power once embedded in the coating.
- Works with the coating you already use: Embed BackBone in RustSeal, Gold Standard Tank Sealer or NuMetal; no fiberglass resin needed.
- One large sheet: Each envelope holds a single 36 x 36 inch piece you cut to the size of each repair.
BackBone (left) lays flat at 0.010 inch thick; a loose mat (right) leaves stiff fibers standing.
BackBone Reinforcing Mesh Technical Data
| Fiber | C-Glass |
|---|
| Binder System | Soluble in Styrene |
|---|
| Structure of Nonwoven | Random |
|---|
| Weight (DIN 53854) | 0.77 oz./yd.2 | 26 g/m2 |
|---|
| Thickness (DIN 53855/1) | 0.010 in. | 0.26 mm |
|---|
| Max. Tensile Strength, Machine Direction (DIN 52857) | 5.6 lbs./2 in. | 25 N/50 mm |
|---|
| Max. Tensile Strength, Across Machine Direction (DIN 52857) | 3.4 lbs./2 in. | 15 N/50 mm |
|---|
| Elongation at Max. Tensile Strength (DIN 53857) | 1% machine direction, 1% across machine direction |
|---|
| Resin Absorption (company specification) | 9.4 oz./yd.2 | 320 g/m2 |
|---|
| Sheet Size | 36 x 36 in. (1 sq. yd.), one piece per envelope |
|---|
BackBone Reinforcing Mesh handles pinholes on its own in RustSeal and, layered with NuMetal Epoxy Putty, non-structural holes up to 3 inches across. KBS recommends a welded metal patch or replacement panel for holes over 3 inches and for any area that is structural or load bearing.
Hole size guide for non-structural repairs
| Pinholes | BackBone in RustSeal, or NuMetal Epoxy Putty |
|---|
| Larger than a pinhole, up to 1/2 inch | NuMetal Epoxy Putty |
|---|
| 1/2 inch to 1 inch | BackBone and NuMetal together |
|---|
| 1 to 3 inches | Several layers of BackBone and NuMetal; back the hole with duct tape |
|---|
| Over 3 inches, or structural | Welded metal patch or replacement panel |
|---|
How far one sheet goes: Cut each patch so the mesh extends 2 to 3 inches past the damaged area on every side. A 1 inch hole takes a patch about 5 to 7 inches square, so one 36 x 36 inch sheet covers many small repairs or one large pan.
Pro Tip: If the hole is over 1 inch in diameter, cover it from the underside with duct tape so BackBone does not sag while the RustSeal dries. Peel the tape off once the patch is dry.
BackBone is applied by embedding a precut piece into a thin, wet 2 mil coat of RustSeal, dabbing it in with a brush, then brushing a second thin coat over it once the first has tacked up. The surface must first be cleaned with KBS Klean, treated with RustBlast and allowed to dry completely.
- Prep: Clean the repair area with KBS Klean, treat it with RustBlast, and let it dry completely.
- Cut: Precut BackBone slightly larger than the area being repaired, using scissors or a razor blade.
- First coat: Brush a thin layer of RustSeal, about 2 mils, on and around the weakened area.
- Embed: Lay the mesh into the wet RustSeal and dab it with your brush until the mesh makes complete contact with the coating.
- Second coat: Once the RustSeal and mesh tack up slightly, brush another thin 2 mil coat of RustSeal, painting outward from the center.
- Cure: Let the patch dry before the next coat. RustSeal is dry to the touch in typically 2 to 6 hours and fully cured 24 hours after the final coat.
Do not let RustSeal pool or puddle over the mesh. Excess RustSeal produces bubbling and poor adhesion; several thin coats build a stronger patch than one heavy coat.
Handling: There is one large piece of cloth in the envelope. Do not handle BackBone with bare hands; always wear gloves. Fibers can fly into the air as you cut the cloth, so wear a mask while cutting.
BackBone Reinforcing Mesh is the choice for pinholes, thin metal and wide or curved areas, because the 36 x 36 inch sheet cuts to any shape and seals inside RustSeal. KBS Patch cures in minutes in sunlight but comes in fixed sizes, and NuMetal Epoxy Putty fills and rebuilds holes that mesh alone cannot bridge.
BackBone compared with KBS Patch and NuMetal Epoxy Putty
| Attribute | BackBone with RustSeal | KBS Patch | NuMetal Epoxy Putty |
|---|
| What it is |
Nonwoven fiberglass mesh embedded in coating |
UV-activated fiberglass patch, adhesive backing |
Two-part epoxy putty, 1:1 hand mix |
| Best for |
Pinholes, thin metal, wide or curved areas |
Fast, sealed patches on tanks, pipes and panels |
Filling and rebuilding holes and cracks |
| Size |
36 x 36 in. sheet, cut to any shape |
3 x 6, 6 x 9 or 9 x 12 in. |
3.5 oz or 1 lb |
| Mixing |
None |
None |
Knead equal parts A and B |
| Cure |
RustSeal dry to touch 2 to 6 hours, full cure 24 hours |
3 to 5 minutes in sun, 30 to 50 minutes cloudy |
Full cure about 12 hours |
KBS Patch is the better choice when the repair has to be finished in minutes and fits a 9 x 12 inch patch, and NuMetal Epoxy Putty alone is better for holes between a pinhole and 1/2 inch. For holes from 1/2 inch to 3 inches, use BackBone and NuMetal together.
BackBone is one step inside the KBS rust repair system. The longest lasting repair follows this order:
- Step 1: KBS Klean
- Removes oil, grease and road grime so the coating bonds.
- Step 2: RustBlast
- Removes rust and etches the metal; let it dry completely.
- Step 3: RustSeal and BackBone
- Embed the mesh in thin coats of RustSeal, then finish with a thin coat over the whole repair area.
- Step 4: Topcoat
- Let the final RustSeal coat cure at least 24 hours, then topcoat any repair that sees sunlight.
See the 3-Step System
BackBone Directions and TDS
Step by step embedding directions, coat thickness and handling notes.
Read Article →
Rocker Panel Rust: How to Fix Hidden Rust and Cab Corners
The hole size guide for choosing mesh, putty or welded metal before you coat.
Read Article →
Trunk and Floorpan Repair Directions
How to mold BackBone into a rusted floor pan or trunk with RustSeal and NuMetal.
Read Article →
Gold Standard Tank Sealer Directions
Exterior tank patching: seal the inside first, then embed BackBone in Tank Sealer outside.
Read Article →
How to Prep Rusty Metal for Paint: The KBS 3 Step System
KBS Klean, RustBlast and RustSeal: the system every BackBone repair sits inside.
Read Article →
Before and After Project Photos
Real customer rust repairs and restorations finished with KBS products.
Read Article →
Have questions before you buy? Find answers to the most common BackBone questions below, or
order BackBone now.
Use BackBone fiberglass mesh when a pinhole, weakened area or small gap is too large to be plugged by RustSeal alone. Embedded in RustSeal, the mesh closes pinholes and reinforces thin metal; layered with NuMetal Epoxy Putty, it rebuilds non-structural holes from 1/2 inch to 3 inches. Holes over 3 inches and structural areas need welded metal or a replacement panel.
BackBone is made for repairing metal, wood and fiberglass with RustSeal, NuMetal Epoxy Putty or Gold Standard Tank Sealer, and KBS does not list concrete reinforcement as a BackBone use. Mesh for concrete, stucco and plaster is a different product sold in rolls by masonry and building suppliers.
Each envelope holds one large piece of BackBone, 1 square yard, which measures 36 x 36 inches unfolded. Cut it to any size or shape with scissors or a razor blade, leaving the mesh 2 to 3 inches larger than the damaged area on every side.
Clean the area with KBS Klean, treat it with RustBlast and let it dry completely. Brush a thin 2 mil coat of RustSeal on and around the area, dab the precut mesh into the wet coating with your brush, then apply a second thin coat outward from the center once the first has tacked up slightly. Do not let RustSeal pool, because heavy coats bubble and lose adhesion.
BackBone in RustSeal handles pinholes. With NuMetal Epoxy Putty, use one layer of mesh for holes from 1/2 inch to 1 inch and several layers for holes from 1 to 3 inches, backing any hole over 1 inch with duct tape so the mesh does not sag. Weld in metal for holes over 3 inches or any structural area.
Yes, on the outside of the tank. Prep both the outside and inside of the repair area and let it dry, seal the inside of the tank with Gold Standard Tank Sealer first, then apply a thin exterior layer of Tank Sealer over the pinholes or weld seams and embed BackBone into it. Patch holes larger than a pinhole with NuMetal Epoxy Putty and let it cure 12 hours before sealing.
RustSeal is dry to the touch in typically 2 to 6 hours, depending on temperature and humidity, and is fully cured 24 hours after the final coat. Let the final RustSeal coat over the BackBone patch cure at least 24 hours before applying a topcoat such as BlackTop.
Yes. Never handle BackBone with bare hands; always wear protective gloves. Fibers can fly into the air as you cut the cloth, so wear a protective mask while cutting to avoid inhaling loose fibers.
No. BackBone, RustSeal and NuMetal are for non-structural repairs such as floor pans, trunk pans, rocker panel skins and cab corners. If the damaged area is structural or load bearing, weld in new metal or replace the panel instead of using mesh or putty.
