The Weather Guard 538-5-02 is a Jumbo underbed box: the same 36" length as a standard box, but a deep 24" body that nearly doubles the room to a full 12.1ft³. That extra depth lets you stand up longer tools and stack bulky gear under the deck of a flatbed, platform or dump body, where a shallow box would run out of space. Heavy welded steel and a gloss black ARMOR TUF finish shrug off road salt and spray, and a weathertight drop-down door keeps everything dry. Mounting hardware is not included, so you can match it to your frame and the added weight.
What's Included:
538 Jumbo Underbed welded steel truck tool box, gloss black
Drop-down door with stainless steel locking compression latch
Three-point latching system with a drill-resistant lock core
Two door support chains that hold the door as a work shelf
Full-perimeter weather seal with rain gutter, pre-installed
Weather Guard installation instructions
Note: mounting brackets and hardware are not included, choose hardware to suit your frame or body
Features
Heavy Welded Steel Body The 538-5-02 is built from heavy welded steel, the toughest and most pry-resistant underbody box Weather Guard makes. It stands up to road spray, debris and the beating an underbed box takes on a work truck, keeping your tools secure and protected.
Gloss Black ARMOR TUF Finish A gloss black ARMOR TUF powder coat covers the welded steel to fight corrosion, chips and fading and give the box a clean, rugged black look. ARMOR TUF is Weather Guard's toughest coating, made to survive the salt, chemicals and weather an underbody box faces.
Weathertight Drop-Down Door A full drop-down door drops open on two support chains that hold it level as a handy work shelf, then closes against a rain gutter and full-perimeter weather seal. Your tools stay dry and protected from road spray, dust and debris in the 12.1ft³ interior.
Stainless Locking Latch, Three-Point Latching A stainless steel locking compression latch drives a three-point latching system with a drill-resistant lock core, so gear stays secure and the door pulls tight against the seal. The latch is easy to work even with gloves on.
Tool-Less QuickClip Door The drop door adjusts from 90 to 180 degrees and pops off with QuickClips, no tools required, so you can drop it flat, use it as a loading shelf, or remove it entirely for full access and clip it back on in seconds.
Mounts Under the Deck, Frees Your Truck The jumbo 24" deep body mounts on the frame rail below a flatbed, platform, service or dump body, so heavy tools and equipment ride secure and out of the way while your deck or bed stays open. It is the way to add locking storage to a truck with no usable bed floor. Mounting hardware is not included so you can match it to your frame.
Gloved-Hand D-Handle and a Wide Door Opening The drop door opens wide, so long tools and cases go in from the side of the deck instead of being lifted over a lip. Weather Guard fits a stainless steel D-handle that is easy to grip with gloves on and pulls the door tight against the seal, and the door itself drops level on its chains to work as a shelf.
Fitment & Compatibility
Application
Fit
Flatbed, platform, stake and dump truck bodies
✓ Yes, mounts under the deck on the frame rail
Service and utility body trucks, enclosed trailers
✓ Yes, where frame-rail space and door clearance allow
Under a full-size pickup bed on the frame rail
✓ Yes, if there is room on the frame and clearance for the door to drop
Standard use inside a pickup bed
✗ No, this box mounts below the bed on the frame, not on the bed floor
Fit guidance: Underbed boxes mount on the truck frame rail below the deck of a flatbed, platform, service or dump body, or under a pickup bed where there is frame space. Fit is by available space and mounting, not by year, make and model. This box is 36" long and 24" deep, and the drop door needs room to swing down below it. Always measure the clear length along your frame rail and the drop clearance before ordering. Mounting brackets and hardware are not included, so plan to supply frame-appropriate mounting hardware.
Specifications
Series: 538 Series Jumbo Underbed
Style: Underbed frame-mount box, single drop-down door
Storage Capacity: 12.1ft³
Exterior Dimensions: 36"L x 24"W x 24"H
Material: Welded steel
Finish: Gloss black ARMOR TUF powder coat
Door: Single drop-down door, tool-less QuickClip hinges, 90 to 180 degrees, two support chains
Overall Size (Weather Guard published): 36-5/8"L x 24-1/4"W x 24-1/8"H
Shipping Size: 37-1/8"L x 24-7/8"W x 24-1/2"H, 110 lb
UPC: 783965042208
Weight: About 110 lb (shipping)
Warranty: Limited Lifetime
Made In: USA
Installation
Type: Frame-rail mount below the deck, bolt-through (hardware not included) · Time: About 1 to 2 hours · Tools: Drill and bits, wrench or socket set, tape measure, marker, plus frame-appropriate mounting brackets and hardware (not included) · Difficulty: Moderate, plan the mounting points and support the box while you bolt it up
Choose a clear spot on the frame rail below the deck with room for the door to drop open, then mount the box to the frame using brackets and hardware rated for the load (not included). Support the box while you fasten it, and seal any drilled holes with zinc-rich primer to prevent rust. Follow the Weather Guard Aluminum and Steel Underbed Boxes installation manual for hole layout and best practices. Because the box hangs below the deck, use hardware and brackets sized for the weight of the box plus its contents.
Resources
Everything you need for your Weather Guard 538 Jumbo Underbed Truck Tool Box, 36" Black Steel, 12.1ft³, in one place.
Warranty. Limited Lifetime Warranty from Weather Guard against defects in materials and workmanship.
Free shipping. This item ships free to the lower 48 states. Because it is an oversized item, it ships by freight and typically arrives in 3 to 7 business days.
Inspect on delivery. Please inspect the packaging before signing. If you see any damage, note it on the delivery receipt and contact us right away, and we will make it right.
Compliance. Mounting brackets and hardware are not included with this underbed box. Because the box mounts on the vehicle frame and carries load below the deck, use mounting hardware and brackets rated for the combined weight of the box and its contents, and confirm clearance so the drop-down door can open safely.
About Weather Guard
Weather Guard has built professional-grade truck and van storage in the USA for decades and is the storage brand tradespeople, contractors, and fleets reach for first. Its steel and aluminum tool boxes, ladder racks, and van-interior systems are engineered to survive daily jobsite abuse and keep expensive tools secure and organized.
Known for weather-tight seals, patented locking systems, and heavy-gauge construction, Weather Guard products mount cleanly on work trucks and vans and stand up to years of hard use. The lineup spans crossover, low-side, and saddle truck boxes, ladder and van racks, drawer units, and fuel and utility tanks, so an entire work vehicle can be outfitted from one brand.
Backed by a strong manufacturer warranty and US-based support, Weather Guard is the name pros trust to protect the tools their livelihood depends on.
Authorized Weather Guard dealer. Prestige Truck is an authorized dealer of Weather Guard, so every tool box, rack and storage product you buy is 100% genuine and factory-new, covered by the full Weather Guard manufacturer warranty, and backed by our own US-based support team.
Compare The Range
How this compares to similar models
The closest alternatives side by side, so you do not have to keep tabs open.
Model
This OneWeather Guard 538 Jumbo Underbed Truck Tool Box, 36 in Black Steel, 12.1 cu ft (538-5-02)
Weather Guard's official step-by-step guide to pulling and replacing a box door, filmed on a high-side box. Weather Guard publishes it on this box's own product page, so keep it bookmarked in case a door ever needs to come off for service or gets damaged on the job.
Best Upgrade for Your Truck
This is Weather Guard's own brand film about outfitting a working pickup, built on the idea that the truck should already be loaded and organized before the day starts. It puts the bed and rail equipment in the context of a real work day rather than a spec sheet.
Watch it if you are still deciding how much storage a truck actually needs. It is the clearest short look at how Weather Guard boxes, racks and drawer units are meant to work together on one vehicle, and it comes straight from the manufacturer rather than a reseller.
Frequently Asked Questions
Straight answers on specs, fit and support
Where and how does this box mount?
It bolts to the frame rail below the deck of a flatbed, platform, service or dump body, or under a pickup bed with frame space. It needs about 36" of rail, and because it is a deep 24" jumbo, confirm there is depth clearance below the deck. Mounting brackets and hardware are not included, so choose hardware rated for the loaded box.
Will it fit my truck?
Fit is by frame-rail space, not year, make and model. The 538-5-02 needs about 36" of clear rail and a deep 24" of clearance below the deck, plus room for the drop door. Measure rail length, depth clearance and drop clearance before ordering, since the jumbo body is taller than a standard box.
Is this steel or aluminum?
This is the welded steel version, the toughest and most pry-resistant underbody box Weather Guard offers, and it weighs about 110 lb. Steel is a great choice for heavy-duty service, flatbed and dump trucks. Weather Guard also builds underbed boxes in lighter aluminum diamond plate if saving weight matters more.
What is the gloss black finish like?
The welded steel body wears a gloss black ARMOR TUF powder coat that resists corrosion, chips and fading and gives a clean, rugged look. Wipe it down with mild soap and water to keep the black finish sharp.
How does the door work and is it weathertight?
The drop-down door lowers on two support chains as a work shelf, seals against a rain gutter and full-perimeter gasket, and locks with a stainless compression latch and three-point latching. The deep 24" jumbo body holds 12.1ft³, so it stays dry and secure while swallowing tall tools and bulky gear a standard box cannot.
Is it made in the USA and under warranty?
Yes. The 538-5-02 is made in the USA and backed by a Weather Guard Limited Lifetime Warranty against defects in materials and workmanship.
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