Finding the best tool box for under tonneau cover use is harder than it sounds. A box may fit your truck bed but still block the cover, rails, or lid.
The safest approach is simple. Measure your available space first. Then choose a box made for your truck and cover style.
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Quick Picks
Best Truck Bed Storage Boxes for Tonneau Covers
Our top picks compared side-by-side — capacity, fit, and compatibility at a glance.
Our Short Verdict
- Choose the UnderCover SwingCase if you want easy tailgate access and minimal loss of bed space.
- Choose the TruXedo TonneauMate if you own a compatible TruXedo cover and a full-size truck.
- Choose the Tuffiom 30-inch box if nothing fits beneath your cover and you can mount a box under the truck.
Will a Tool Box Fit Under Your Tonneau Cover?
A tool box can fit under a tonneau cover. However, truck beds and cover designs are not all the same.
You must check more than the box height. Cover rails, support bows, hinges, and rolled cover material can all reduce space.
Use these steps before ordering.
Step 1: Measure Your Vertical Clearance
Close your tonneau cover. Measure from the truck bed floor to the lowest part beneath the cover.
That lowest part may be:
- A side rail
- A support bow
- A folding panel
- A retractable cover canister
- A rolled cover near the cab
Measure in several spots. The space near the tailgate may differ from the space near the cab.
Use the smallest measurement as your real limit. Leave a little extra room instead of buying a box with an exact fit.
Step 2: Measure Your Usable Bed Space
Check the width between the wheel wells. Then measure the open floor length.
You should also measure:
- The gap behind each wheel well
- The wheel-well height
- The space between the wheel well and tailgate
- The distance between the cover rails
- The space used by a retractable cover canister
Do not rely only on your truck’s listed bed size. Rails and cover parts can reduce the usable room.
Step 3: Compare the Box Dimensions
Compare your measurements with the box’s exterior size. Do not use its inside storage dimensions.
Pay close attention to:
- Total exterior height
- Lid height when open
- Hinge position
- Mounting brackets
- Handle or lock clearance
- Space needed to swing or lower the door
A box can fit beneath the closed cover yet still be hard to open. This is common with top-opening boxes.
Step 4: Check Lid and Door Access
Think about how you will reach your tools.
Can you open the box while the cover stays closed? Must you roll or fold the cover first? Will the rolled cover block the lid?
Side-opening and swing-out boxes can avoid some of these issues. A top lid needs more open space above the box.
Watch the Headboard Gap
A roll-up cover gathers near the front of the bed. That bundle may take up space above a front-mounted tool box.
One TonneauMate buyer found the lid hard to open when the cover was fully rolled forward. This may not happen with every truck and cover.
Still, it is worth checking before you mount the box.
Fit tip: Dry-fit the box before drilling or tightening the clamps. Close, roll, and open the cover to test every position.
Tonneau Cover Type vs Tool Box Type
The chart below is a starting point. Your exact truck, cover, box model, and mounting hardware still control the final fit.
Tonneau Cover & Box Compatibility Matrix
Find the right storage box style based on your current truck bed cover setup.
| Cover Type | Swing-Out Box | TonneauMate Style | Low Bed-Floor Box | Underbody Box |
|---|---|---|---|---|
| Soft Roll-Up | ✅ Often a good match | ⭐ Best with listed models | 📏 Depends on height | ✔️ Not affected by cover |
| Soft Tri-Fold | 🔍 May work by model | 📋 Check cover & box details | 📏 Depends on height & lid | ✔️ Not affected by cover |
| Hard Tri-Fold | 🔍 Check exact box & cover | ⚠️ Often not the best pairing | 📏 Depends on panel clearance | ✔️ Not affected by cover |
| Hard / Quad-Fold | 🔍 Check model carefully | 📞 Check with cover maker | 📏 Depends on folded space | ✔️ Not affected by cover |
| Retractable | 📐 Check space by wheel well | ⚠️ Canister may block mount | ⚠️ Canister reduces bed space | ✔️ Not affected by cover |
| One-Piece Hinged | 🔍 Check opening clearance | 📋 Check rail & lid clearance | 🔑 Height & lid access key | ✔️ Not affected by cover |
| Cover w/ Sport Bars | 🚫 Often difficult fit | ⚠️ Rails may conflict | 📐 Measure every obstacle | ✔️ Not affected by cover |
UnderCover says the SwingCase works with many soft, hard, folding, and rolling covers. It also states that three inches of clearance are needed.
However, compatibility can change by SwingCase model. One truck-specific version may not work with the same covers as another.
Check the exact stock number before buying.
What Not to Buy
The wrong box can stop your cover from closing. It can also damage the rails or create a costly return.
A Tall Crossover Box
A standard crossover box sits across the bed near the cab. Many models rest on top of the bed rails.
That design often conflicts with tonneau cover rails. It may also sit too high for the cover to close.
Do not assume “low profile” means “fits under a tonneau cover.” Check the full exterior height.
A Deep Bed Chest Without Measuring
A chest may fit between the wheel wells. Yet its lid can still hit the cover.
You need enough room for both the box and its open lid. A side-opening box may work better in a tight space.
The Wrong SwingCase Side
SwingCase boxes are sold for a specific truck and side. Driver-side and passenger-side boxes are separate.
A box made for the wrong side will not mount as planned. Always choose your exact truck, model year, and side.
A Full-Size TonneauMate for a Smaller Truck
The TonneauMate is designed for most full-size trucks. It is not a general fit for every pickup.
It excludes flareside, stepside, and composite beds. Check your bed design before ordering.
An Underbody Box Treated as an In-Bed Box
Some boxes are meant for underbody, flatbed-side, or similar mounting. They are not direct replacements for a normal in-bed chest.
Mounting one may require custom planning. You must also account for ground clearance and road spray.
Best Tool Box for Under Tonneau Cover: Our Three Picks
We limited this list to three distinct solutions. Each one suits a different truck setup.
We compared listed specifications, fit information, and owner feedback. We did not perform hands-on tests.
1. UnderCover SwingCase: Best Overall for Most Tonneau Owners
The UnderCover SwingCase is our best overall choice because it uses space that often goes unused. It sits between the rear wheel well and tailgate.
Pull the release, and the box swings over the open tailgate. This lets you reach your tools without climbing into the bed.
Key Facts
| Feature | Details |
|---|---|
| Type | Swing-out bedside tool box |
| Location | Between the rear wheel well and tailgate |
| Size | Varies by truck; listed examples include 8.5 by 34 inches and 10 by 36 inches |
| Material | ABS plastic |
| Capacity | Up to 75 pounds per box |
| Security | Lockable lid with twist lock |
| Weather protection | Moisture seal |
| Release | Quick-release latch |
| Installation | Drilling required |
| Cover clearance | UnderCover says three inches |
| Warranty | One year |
| Fit | Vehicle, model year, and side-specific |
Why It Works Well
The SwingCase does not take over the whole front of your truck bed. Long items can still run along much of the bed floor.
Its swing-out design also improves access. You can bring the box toward you instead of reaching over the bed wall.
The twist lock can open with or without a key. The lid also has a moisture seal, though you should not treat the box as fully waterproof.
Pros
- Uses the space behind the wheel well
- Swings over the tailgate for easy access
- Holds up to 75 pounds per box
- Has a lockable lid
- Includes a moisture seal
- Can be removed through its quick-release system
- Leaves much of the bed open
Cons
- Requires drilling into the truck bed
- Size changes based on the truck
- Driver and passenger boxes are separate
- Cover compatibility can vary by model
- ABS plastic may not suit buyers who want a metal box
Fit Warning
UnderCover says the box works with many tonneau cover styles and needs three inches of clearance. Still, at least one truck-specific listing excludes UnderCover folding covers.
Confirm compatibility for the exact box you plan to buy. Do not rely on a claim made for another SwingCase model.
Who Should Skip It?
Skip this box if you do not want to drill into your bed. It is also less useful if you need one large storage area across the front.
Select your exact truck and preferred side on the Amazon page before ordering.
2. TruXedo TonneauMate: Best for TruXedo Soft Covers and Full-Size Trucks
The TruXedo TonneauMate is a better fit for larger tool loads. It clamps to the bed rails and sits above the bed floor.
You can mount it near the front, middle, or rear. Its raised design also leaves room to slide lumber beneath it.
Key Facts
| Feature | Details |
|---|---|
| Model | 1117416 |
| Exterior dimensions | About 55.38 by 22.25 by 14.75 inches |
| Rounded maker dimensions | 55 by 22 by 15 inches |
| Interior dimensions | 43 by 14.5 by 13 inches |
| Capacity | 10 cubic feet |
| Load capacity | 200 pounds |
| Material | Aluminum and composite |
| Lid | Single-lid design |
| Lock | Stainless steel keyed lock with two keys |
| Mounting | Clamps to bed rails |
| Drilling | Not required |
| Truck fit | Most full-size trucks |
| Warranty | Two years |
Cover Compatibility
The TonneauMate is designed for these TruXedo covers:
- Pro X15
- Lo Pro
- TruXport
- Sentry
- Deuce
It can also be used without a cover. It works best with soft or hard roll-up styles.
The exact setup still matters. Measure the box height against the lowest part of your closed cover.
Why It Works Well
The TonneauMate gives you more storage than a small swing-out box. Its 200-pound capacity may suit larger tool sets.
Its clamp-on design is another benefit. You can install it without drilling into the bed.
You can also choose where it sits. Front, middle, and rear mounting can suit different cargo needs.
Pros
- Offers 10 cubic feet of storage
- Holds up to 200 pounds
- Requires no drilling
- Can mount in several bed positions
- Leaves room for lumber below
- Includes a keyed stainless steel lock
- Designed for several TruXedo covers
Cons
- Intended for full-size trucks
- Does not fit flareside, stepside, or composite beds
- Track-system bed clamps are not included
- A rolled cover may limit lid access
- Takes more bed width than a swing-out box
Fit Warning
Check the space near the cab if you plan to mount the box at the front. A fully rolled cover may sit above the lid.
One buyer reported that this made the lid hard to open. Test that movement before final installation.
Who Should Skip It?
Skip the TonneauMate if you own a midsize truck. You should also skip it if your bed is flareside, stepside, or composite.
Owners of track-system beds should note that the needed clamp kit is not included.
3. Tuffiom 30-Inch Aluminum Truck Box: Budget Underbody Alternative
The Tuffiom is not an under-tonneau box. It belongs in this guide as a skip-the-bed option.
Consider it when your cover leaves too little room. It may also help when you want to keep the whole bed open.
Key Facts
| Feature | Details |
|---|---|
| Type | Aluminum truck box |
| Length | 30 inches |
| Capacity | Listed at 4.2 cubic feet |
| Material | Aluminum |
| Access | Fold-down side door |
| Latch | Key-lockable twist latch |
| Suggested placement | Near the tailgate or on the side of a flatbed |
| Use in this guide | Underbody or skip-the-bed alternative |
Why It May Work
The fold-down side door does not need top-lid clearance. That can help in a tight mounting spot.
The aluminum build also keeps rust concerns lower than bare steel. Even so, mounting location and road exposure still matter.
One review praised its build for the price. The reviewer’s minor complaint was that the latch needed some jiggling to lock tightly.
Pros
- Keeps storage out of the covered bed
- Uses a side door rather than a top lid
- Offers 4.2 cubic feet of space
- Has a key-lockable latch
- Aluminum will not rust like untreated steel
Cons
- Installation may require custom brackets or drilling
- Underbody use exposes it to road spray and dirt
- Poor placement may reduce ground clearance
- The latch may need adjustment or jiggling
- Security depends on the box and mount location
Underbody Fit Warning
Do not mount this box based on its 30-inch length alone. Check the full mounting area beneath your truck.
The box must remain clear of moving, hot, and low-hanging parts. A secure mount is vital.
If you are unsure about the location, use a qualified installer. This is not the same job as placing a loose chest in the bed.
Who Should Skip It?
Skip this choice if you want a simple clamp-on install. It is also a poor fit if your truck has little safe space beneath the body.
How to Choose the Right Box
The best choice depends on your tools, truck, and cover. Use these points to narrow it down.
Material
Aluminum resists rust and keeps weight lower. Steel is often strong but may rust if its finish gets damaged.
ABS plastic does not rust. It can also work well for small bedside boxes.
Material alone does not prove that a box is strong or weatherproof. Check the listed load limit and warranty.
Lock and Weather Seal
A lock can slow down a thief. It does not make the box impossible to break into.
Look for a secure latch and a good seal. Use “water-resistant” unless the maker clearly promises full waterproofing.
Underbody boxes need more care. They face road spray, dust, mud, and salt.
Capacity
Think about what you carry most often. Small hand tools need less room than power tools and recovery gear.
Do not compare storage volume alone. Check the listed weight limit too.
A large box becomes less useful if its load limit is too low for your tools.
Mounting Method
The SwingCase requires drilling. The TonneauMate clamps to the bed rails without drilling.
An underbody box may need brackets and custom mounting work. Pick the method you feel safe using.
Access
Ask one key question: Can you reach your tools without fighting the cover?
A swing-out box brings the tools to the tailgate. A rail-mounted box may require you to roll back the cover.
An underbody box keeps the bed free but moves tool access outside it.
Warranty and Return Terms
Check the current warranty and Amazon return terms before buying. Return rules can differ by seller and product condition.
Keep the packaging until you finish your fit check. Do not drill until you know the box works.
Installation and Fit-Check Tips
A few checks can prevent a bad install.
- Inspect the box before mounting it. Check the lid, lock, seal, and latch.
- Place it in the planned location. Do not drill or tighten clamps yet.
- Close the tonneau cover. Look for contact with rails, bows, and panels.
- Open the box. Make sure the lid or door has room to move.
- Roll or fold the cover. Test every normal cover position.
- Load a few common tools. Confirm that you can still reach them.
- Finish the installation. Follow the maker’s instructions for your model.
Stop if the cover presses against the box. Constant contact may damage the cover or its frame.
Don’t Need a Hard Box?
A hard tool box is not your only choice.
Soft bags and truck bed organizers fit beneath many low covers. They are easier to remove and often need no mounting.
Storage totes can also work for groceries, sports gear, or light tools. Choose a tote that will not slide around the bed.
Ford Maverick owners should use a truck-specific guide, like our 7 Best Tool Boxes for Ford Maverick. Its smaller bed creates different fit limits than a full-size truck.
Whichever box you pick, it’s the natural home for roadside basics like jumper cables, a tow strap, and a flashlight. Not sure what to pack? Our car emergency kit guide covers what to keep in your vehicle and why.
Quick Decision Guide
- You want easy tailgate access: Choose the UnderCover SwingCase.
- You want to keep most of the floor open: Choose the SwingCase.
- You own a listed TruXedo cover: Consider the TonneauMate.
- You carry a larger tool load: Compare your setup with the TonneauMate.
- You refuse to drill into the bed: The TonneauMate uses clamps.
- You have very little space beneath the cover: Consider an underbody setup.
- You need the whole bed for cargo: Consider the Tuffiom as a skip-the-bed option.
- You own a midsize truck: Do not assume the full-size TonneauMate will fit.
- You have a folding cover: Confirm the exact SwingCase stock number before buying.
Frequently Asked Questions
Can I Put a Tool Box Under a Tonneau Cover?
Yes, if the box fits beneath the cover and does not block its rails. Measure height, width, length, and opening space first. You should also check how the cover folds or rolls. Truck-specific boxes are often easier to match than universal models.
How Much Clearance Do I Need Under a Tonneau Cover?
You need more space than the tool box’s total exterior height. Leave a margin so the cover does not rub against it. UnderCover says its SwingCase needs three inches of clearance. Other boxes have different needs, so check the maker’s specifications.
Can I Use a Crossover Tool Box With a Tonneau Cover?
Sometimes, but many crossover boxes sit on top of the bed rails. This can block tonneau cover hardware. A tall box may also stop the cover from closing. Only buy one after both the cover maker and box maker confirm the fit.
Can I Reach My Tools With the Cover Closed?
That depends on the box design. A SwingCase swings toward the tailgate, which improves access. A top-opening box may require you to roll or fold the cover first. Test both the cover and box before final mounting.
Does a Roll-Up Cover Work With a Tool Box?
It can. The SwingCase works with many roll-up covers, depending on the exact model. The TonneauMate is designed for several TruXedo roll-up covers. Check where the rolled cover rests because it may block a top lid.
Are Under-Tonneau Tool Boxes Waterproof?
Do not assume they are waterproof. Some have moisture seals or water-resistant designs. Water may still enter during heavy rain, washing, or road spray. Store sensitive items in sealed bags or small cases inside the box.
Can I Mount a Tool Box Under the Truck?
An underbody box can keep your truck bed open. However, the install is more involved. You must consider mounting strength, road spray, security, heat, moving parts, and ground clearance. Use a qualified installer if you cannot confirm a safe location.
How We Picked
We compared manufacturer specifications, fit information, product listings, and owner review themes.
We focused on three useful options:
- A truck-specific swing-out box
- A full-size under-cover box
- An underbody alternative
We did not claim hands-on testing. You should confirm fit for your truck, cover, model year, and chosen side before ordering.
Final Verdict
The UnderCover SwingCase is the best overall choice for most tonneau owners. It saves floor space and provides easy tailgate access. Just select the correct truck and side.
The TruXedo TonneauMate suits full-size trucks with a compatible TruXedo cover. It offers more storage and uses no-drill clamps.
If neither fits, the Tuffiom 30-inch aluminum box offers another path. Mounting it outside the bed avoids tonneau clearance issues, but installation needs more care.
Measure first. Check the exact model. Then dry-fit everything before drilling.
Planning a long haul with your truck? Once the bed is sorted, set up the cab for comfort, safety, and storage by zone so everything stays within easy reach.