The Weather Guard 631-0-02 is a 30" aluminum underbed box, a versatile mid-small size that adds room while keeping weight low. The welded diamond-plate body is 18" deep, holds 5.4ft³, and its bright clear ARMOR TUF finish and rust-proof aluminum stand up to road salt on a flatbed, platform or dump body. A weathertight drop-down door keeps a fuller service kit, tools and chains dry, and the 30" length still leaves rail for a second box. Mounting hardware is not included, so you can match it to your frame.
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
Lightweight Aluminum Diamond Plate The 631-0-02 is formed from welded aluminum diamond plate, so it adds locking underbody storage without the weight of steel. Aluminum naturally resists rust and corrosion, which matters for a box that lives down near the road spray and salt.
Clear ARMOR TUF Diamond Plate A clear ARMOR TUF powder coat covers the aluminum diamond plate to fight corrosion, chips and fading and give the box a classic bright diamond-plate 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 5.4ft³ 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 standard 18" 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 on the 631-0-02 opens to a clear 13-1/2" high by 25-1/4" wide opening, 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 30" long and 18" 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: 631 Series Underbed
Style: Underbed frame-mount box, single drop-down door
Storage Capacity: 5.4ft³
Exterior Dimensions: 30"L x 18"W x 18"H
Door Opening: 13-1/2" high x 25-1/4" wide
Material: Welded aluminum diamond plate
Finish: Clear 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): 30-1/8"L x 18"W x 18"H
Shipping Size: 30-3/4"L x 18-7/8"W x 18-1/2"H, 39 lb
UPC: 783965042017
Weight: About 42 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 631 Underbed Truck Tool Box, 30" Bright Aluminum, 5.4ft³, 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 631 Underbed Truck Tool Box, 30 in Bright Aluminum, 5.4 cu ft (631-0-02)
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. At 30" long it fits medium runs of rail. Mounting brackets and hardware are not included, so choose hardware rated for the box plus its contents.
Will it fit my truck?
Fit is by frame-rail space, not year, make and model. The 631-0-02 needs about 30" of clear rail and 18" of depth, plus room below for the drop door. Measure the clear rail length and drop clearance before ordering.
How much does it weigh and will it corrode?
It is built from welded aluminum diamond plate and weighs only about 42 lb, much lighter than a comparable steel box, which is easier on your frame and payload. Aluminum naturally resists rust, an advantage for a box that lives down near road spray and salt, and it stays secure with a drill-resistant locking latch.
What is the bright aluminum finish like?
The aluminum diamond plate wears a clear ARMOR TUF coat that shows the bright tread pattern while sealing out corrosion. It cleans up fast and gives a classic work-truck look that holds up to road salt.
How does the door work and is it weathertight?
The drop-down door opens a 25-1/4" wide by 13-1/2" tall mouth and lowers on two support chains as a work shelf. It seals against a rain gutter and full-perimeter gasket and locks with a stainless compression latch and three-point latching, keeping the 5.4ft³ interior dry and secure, room enough for a service kit and hand tools.
Is it made in the USA and under warranty?
Yes. The 631-0-02 is made in the USA and backed by a Weather Guard Limited Lifetime Warranty against defects in materials and workmanship.
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