What is the Schutz Underseal Spray Gun?
The Schutz Underseal Spray Gun is an air-powered applicator gun that sprays undercoatings, cavity waxes, and bed liners directly from a standard US dome-style quart can at 45 to 150 PSI. The included 48-inch flexible extension probe carries a 360-degree spray tip that reaches inside boxed frames, rocker panels, and door skins through a 3/8-inch access hole.
45-150 PSI
Working Pressure Range
48"
360-Degree Wand Reach
3/8"
Access Hole Required
1/4" NPT
Air Inlet Fitting
The Schutz Underseal Spray Gun body is machined from nickel-plated aluminum, so the solvents in undercoatings and cavity waxes do not attack it and the gun survives repeated cleaning cycles. An adjusting screw at the nozzle opens or closes the spray pattern, which is how texture is dialed in when spraying KBS UnderCoat: lower pressure lays down a coarser, more traditional undercoating texture, higher pressure lays down a finer one.
Because the gun threads onto a standard US dome-style quart can, there is no cup to fill and no funnel step. A quart of KBS UnderCoat or thinned Cavity Coater goes straight onto the gun, and coating that is left over stays sealed in its own can between sessions.
One gun handles the whole rust-proofing job: cavity wax inside the frame, undercoating underneath it, bed liner on top of it. Satisfaction guaranteed!
The gun ships with the 48-inch flexible probe and 360-degree tip. The tip passes through a 3/8-inch hole, so no panel surgery is needed to reach an enclosed cavity.
The Schutz Underseal Spray Gun sprays KBS UnderCoat, KBS Bed Liner, KBS Cavity Coater, and other corrosion inhibitors, cavity waxes, undercoatings, and bed liners packaged in dome-style quart cans. The 48-inch wand attachment is limited to thin, low-viscosity coatings such as Cavity Coater thinned 30 to 50 percent; thicker products go through the standard spray nozzle instead.
- KBS Cavity Coater — The gun and 48-inch wand are the recommended way to get Cavity Coater into boxed frames, door bottoms, rocker panels, and floor seams. Thin Cavity Coater 30 to 50 percent with KBS #1 Thinner or mineral spirits before spraying.
- KBS UnderCoat — Both the solvent-based and waterbased undercoatings spray through the standard nozzle. Thinning is not usually needed. Adjust pressure at the gun to control how coarse the finished texture is.
- KBS Bed Liner — Sprays through the standard nozzle for truck beds, tailgates, and interior floor pans where a textured, high-build film is wanted.
- Cavity waxes and corrosion inhibitors — Any thin, wicking cavity wax of similar viscosity to thinned Cavity Coater can go through the 48-inch probe.
- Third-party undercoatings — The gun accepts any standard US dome-style quart can, so it is not limited to KBS products.
- Not for the wand: thick coatings — The 48-inch probe is not designed to spray KBS UnderCoat, KBS Bed Liner, or any other high-viscosity coating. Forcing thick material through the small-bore probe clogs the 360-degree tip.
Can the Schutz Gun Spray Bed Liner and Undercoating Through the 48-inch Wand?
No. The 48-inch extension probe is sized for thin, viscous coatings only, which in practice means Cavity Coater and similar cavity waxes thinned 30 to 50 percent. KBS UnderCoat and KBS Bed Liner are sprayed through the gun's standard nozzle, not the wand. The wand and the nozzle are two separate application paths on the same gun.
The Schutz Underseal Spray Gun combines three things a general-purpose spray gun does not have: a nickel-plated aluminum body that resists coating solvents, an adjusting screw that changes undercoating texture on the fly, and a 48-inch 360-degree probe that coats the full inside circumference of a cavity from a single 3/8-inch hole.
- Nickel-Plated Aluminum Body: Solvent-resistant and light enough to hold overhead while coating a floor pan or frame rail. Nickel plating keeps the internal passages from corroding between jobs.
- 45 to 150 PSI Working Range: Runs off any shop compressor. Lower pressure builds a coarser undercoating texture, higher pressure atomizes finer for cavity wax.
- 1/4-inch NPT Air Inlet: The standard automotive shop fitting, so the gun connects to an existing air line with no adapter.
- Fits Standard US Dome Quart Cans: Threads directly onto the can. No transfer pot, no funnel, and unused coating stays sealed in its original can.
- Adjusting Screw for Spray Pattern: One screw sets the pattern for the viscosity of whatever is loaded, from thinned cavity wax to full-bodied bed liner.
- Smooth Trigger Action: Progressive trigger control lays coatings down in even layers rather than heavy bursts that run and sag.
- 48-inch Flexible 360-Degree Probe: Feeds around bends inside a boxed frame and sprays the full circumference of the cavity in one pass rather than only the wall it is pointed at.
- 3/8-inch Access Hole: The spray tip passes through a 3/8-inch hole, small enough to plug with a body grommet afterward.
- Easy to Clean and Reusable: Flush with KBS #1 Thinner or mineral spirits right after use and the gun goes back on the shelf ready for the next job.
The Schutz Underseal Spray Gun is built for rustproofing vehicle bodies: enclosed cavities that trap moisture, exposed underbody surfaces that take road salt and stone chips, and truck beds. The 48-inch probe handles anything hollow that can be reached through a 3/8-inch hole, and the standard nozzle handles everything on the outside.
- Enclosed Body Cavities
- Boxed frame rails, rocker panels, cab corners, door bottoms, quarter panels, and tailgate shells. These are the areas that rust from the inside out and cannot be reached with a brush.
- Underbody and Chassis
- Wheel wells, floor pans, frame surfaces, and inner fenders sprayed with KBS UnderCoat for road-salt and stone-chip protection plus sound deadening.
- Truck Beds and Tailgates
- KBS Bed Liner sprayed through the standard nozzle for a textured, impact-resistant surface on beds, tailgates, and utility trailer decks.
- Weld Seams and Overlapping Panels
- Cavity Coater wicks into pinch welds, spot-welded flanges, and floor seams where two panels trap moisture between them.
- Restoration and Bodywork
- Freshly repaired panels get cavity wax on the inside before the outside is sealed up, which is the step most restorations skip and later regret.
- Trailers, Equipment, and Farm Machinery
- Any hollow steel section on a trailer frame, mower deck, or implement that sits outside and holds water.
Ventilation warning: When coating is sprayed into an enclosed area such as a door panel, the solvents may take several hours to escape. Keep the enclosed area away from heat, sparks, electrical devices, and open flames during that time, and always work in a well-ventilated space with gloves and safety glasses.
The Schutz Underseal Spray Gun operates anywhere from 45 to 150 PSI, and the right setting depends on the coating. KBS Cavity Coater sprays at 90 to 150 PSI at the gun after being thinned 30 to 50 percent with KBS #1 Thinner or mineral spirits. KBS UnderCoat sprays unthinned, with pressure used to set the finished texture.
| Coating | Path | Pressure at Gun | Thinning |
|---|
| KBS Cavity Coater | 48-inch wand | 90 to 150 PSI | Thin 30 to 50% with KBS #1 Thinner or mineral spirits |
| KBS UnderCoat (solvent) | Standard nozzle | 45 to 150 PSI, set for texture | Not usually needed; thin with KBS #1 Thinner |
| KBS UnderCoat (waterbased) | Standard nozzle | 45 to 150 PSI, set for texture | Not usually needed; thin with water |
| KBS Bed Liner | Standard nozzle | 45 to 150 PSI, set for texture | Not usually needed |
Air consumption: 13.5 SCFM through the standard spray nozzle, 6.5 SCFM through the 48-inch extension probe. Check that the compressor can sustain 13.5 SCFM before starting a full underbody job.
How Do You Get an Even 1-Mil Film Inside a Frame Rail?
Stir the thinned Cavity Coater 3 to 5 minutes until the mixture is uniform, insert the 48-inch probe to the far end of the cavity, then depress the tip and withdraw the probe at roughly one foot per second. A 1-mil dry film is the target. Varying air pressure and withdrawal speed is how coverage gets dialed in on the first cavity.
Pro Tip: Clean the gun the moment the job is done, not the next morning. Run KBS #1 Thinner or mineral spirits through both the nozzle and the probe until it sprays clear. Cured undercoating inside the 360-degree tip is the one failure this gun actually has, and it is entirely preventable.
The Schutz Underseal Spray Gun and a Cavity Coater aerosol with a Cavity Wand do the same job at different scales: the aerosol is self-contained and needs no compressor, while the Schutz gun runs bulk quarts, adjusts spray texture, and sprays undercoating and bed liner that no aerosol delivers. Both put a 1-mil film inside a cavity.
| | Schutz Underseal Gun | Aerosol Can + Cavity Wand |
|---|
| Air compressor required | Yes, 45 to 150 PSI at 13.5 SCFM | No |
| Coating supply | Bulk quart cans, refillable | Single aerosol can |
| Sprays undercoating and bed liner | Yes, through the standard nozzle | No, cavity wax only |
| Adjustable spray texture | Yes, adjusting screw plus pressure | No, fixed aerosol pattern |
| Reach into cavities | 48-inch 360-degree probe | Cavity Wand, shorter reach |
| Thinning required | Yes for Cavity Coater, 30 to 50% | No, aerosol is ready to spray |
The aerosol and Cavity Wand are the better choice for a single door or a couple of rocker panels, where hauling out a compressor and then cleaning a gun costs more time than the job itself. The Schutz gun earns its keep once the work is a full underbody, a whole frame, or any job that also needs undercoating sprayed.
Clean the Schutz Underseal Spray Gun immediately after use, before the coating begins to set. Flush KBS #1 Thinner or mineral spirits through the gun and out the nozzle until the spray runs clear, then flush the 48-inch probe the same way. Waterbased KBS UnderCoat cleans up with soap and water instead.
- Step 1 — Empty the can
- Unthread the coating can and return any usable material to a sealed container.
- Step 2 — Flush the nozzle
- Thread on a can of KBS #1 Thinner or mineral spirits and spray until the output is clear. For waterbased UnderCoat, use soap and water.
- Step 3 — Flush the probe
- Attach the 48-inch probe and repeat, so solvent passes through the full length of the wand and out the 360-degree tip.
- Step 4 — Wipe overspray
- Remove excess coating from the vehicle with a clean rag lightly dampened in mineral spirits. Do not soak the rag.
Shop KBS #1 Thinner
Coat the inside before the outside. Spray KBS Cavity Coater into the enclosed cavities through the 48-inch probe, let the solvents flash off, then switch to the standard nozzle and lay KBS UnderCoat over the underbody. Cavity Coater is applied after paints and coatings have fully cured and is never painted over.
For the ultimate rust protection: treat bare metal with KBS RustSeal before applying KBS UnderCoat. UnderCoat has excellent adhesion to cured RustSeal.
Cavity Wax Provides Rust Protection in Hard-to-Reach Areas
Why enclosed cavities rust from the inside out, and how cavity wax sprayed through a wand stops it.
Read Article →
Cavity Coater Directions and Technical Data Sheet
Full spray procedure for the Schutz gun: thinning ratio, 90 to 150 PSI, stir time, and 1-mil film target.
Read Article →
KBS UnderCoat Directions and Technical Data Sheet
Spray directions, coverage figures, and cleanup for solvent-based and waterbased UnderCoat through this gun.
Read Article →
How To Prepare Metal Before Body Work To Prevent Future Rust
The prep sequence that decides whether a repaired panel stays solid or rusts again from behind.
Read Article →
KBS Instructional Videos
Free how-to videos covering cavity coating, undercoating, bed liner, and full rust prevention.
Watch Videos →
Before and After Photos
Real customer underbody, frame, and bed restorations done with KBS coatings.
View Gallery →
Have questions before you buy? Find answers to the most common Schutz Underseal Spray Gun questions below, or
order the gun now and get it shipped same day.
The Schutz Underseal Spray Gun is an air-powered applicator that threads onto a standard US dome-style quart can and sprays undercoatings, cavity waxes, and bed liners at 45 to 150 PSI. What sets it apart from a general spray gun is the combination of a solvent-resistant nickel-plated aluminum body, an adjusting screw that changes the finished undercoating texture, and the included 48-inch flexible probe with a 360-degree tip that coats the full inside of a cavity through a 3/8-inch hole.
The gun sprays KBS Cavity Coater, KBS UnderCoat in both solvent-based and waterbased versions, KBS Bed Liner, and other corrosion inhibitors, cavity waxes, undercoatings, and bed liners supplied in standard US dome-style quart cans. Thick coatings go through the standard nozzle. Only thin, low-viscosity coatings such as thinned Cavity Coater go through the 48-inch extension probe.
No. The 48-inch spray wand attachment is designed for Cavity Coater and other thin, viscous coatings only. It is not designed to spray KBS UnderCoat, KBS Bed Liner, or any other thicker coating, because high-viscosity material clogs the small-bore probe and the 360-degree tip. Spray those products through the gun's standard nozzle instead.
The gun's working pressure range is 45 to 150 PSI through a 1/4-inch NPT air inlet. For Cavity Coater, KBS recommends 90 to 150 PSI at the gun. Air consumption is 13.5 SCFM with the standard spray nozzle and 6.5 SCFM with the 48-inch extension probe, so confirm the compressor can sustain 13.5 SCFM before starting a full underbody job.
Yes. Thin Cavity Coater 30 to 50 percent with KBS #1 Thinner or mineral spirits as needed, then stir the mixture for 3 to 5 minutes until it reaches a homogeneous state before spraying. KBS UnderCoat does not usually need thinning, but it can be thinned with KBS #1 Thinner if solvent-based or with water if waterbased.
The spray tip of the 48-inch wand requires just a 3/8-inch hole. That is small enough to close afterward with a standard body grommet or plug, so a boxed frame rail or rocker panel can be coated internally without cutting an access panel.
Texture is set two ways: the adjusting screw at the nozzle opens or closes the spray pattern for the viscosity of the coating loaded, and air pressure changes how finely the material atomizes. Lower pressure produces a coarser, more traditional undercoating texture; higher pressure produces a finer, smoother one. Test on cardboard before spraying the vehicle.
Clean the gun right after use. Flush KBS #1 Thinner or mineral spirits through the standard nozzle until the spray runs clear, then attach the 48-inch probe and flush it the same way so solvent passes out through the 360-degree tip. Waterbased KBS UnderCoat cleans up with soap and water. The gun is very easy to clean when it is done immediately; cured coating inside the tip is far harder to remove later.
The package includes the Schutz Underseal Gun and a 48-inch flexible extension probe fitted with a 360-degree spray tip, designed for Cavity Coater and other thin, viscous coatings. An empty dome-style quart can is offered as a separate option at checkout for anyone who wants to decant bulk coating or keep a thinned batch ready.
Yes, with proper precautions. When coating is sprayed into an enclosed area such as a door panel, the solvents may require several hours to escape. During that time the enclosed area must be kept away from heat, sparks, electrical devices, and open flames that could ignite vapors. Always work in a well-ventilated area and wear protective gloves and safety glasses.
