Best Tool Box for Under a Tonneau Cover: What Clears a Closed Cover

How we made this guide: picks and specs come from our catalog and fitment data, owner quotes come from verified reviews and the guide was drafted with AI help, then checked and edited by Trevor Hall.

The best tool box for under a tonneau cover in our range is the Weather Guard 614 compact chest (from $885), the shortest chest we carry, followed by the larger 664 chest (from $978) and, where the frame has room, the 548 underbed box (from $930). The budget pick is the UnderCover SwingCase (from $219.99), a small box that bolts to the bed side over the wheel arch.

Height decides which boxes work. The boxes in our truck tool boxes collection are all Weather Guard, and this guide compares seven of them, 13 to 19-1/4 inches tall and starting between $885 and $1,293.

Every box side by side

The height test: will the box clear your cover?

A cover rides on the bed rails, so a box inside the bed must stay below them and clear the underside of the cover.

1. Find your truck below, or measure from the floor to the top of the bed wall with your liner in.
2. Subtract the box height (16-1/4 inches for the 614, 19-1/4 for the 664) to get the room left above the closed lid.
3. Measure how far the lowest part of your cover, such as its rails or cross bows, hangs below the rail line. If that is less than the room left, the lid clears.

These figures come before your liner and cover, and cover heights differ, so we do not state them. For the Colorado and the 2024 to 2026 Tacoma, use our truck bed measuring guide.

How we picked

Picks use our catalog, not truck testing: listed specs, the trucks each box is listed for, OEM bed depths and owner reviews. Only the SwingCase (141 reviews), the 664 (20), the 174 (16) and the 548 (7) have more than three, so the other picks lean on spec sheets.

Best overall: Weather Guard 614 compact chest

The 614 is a chest tool box for the bed floor: 7.0 cubic feet in a 40 by 20 inch body, 16-1/4 inches tall. It leaves 2.85 to 6.15 inches below the rail line in the table above, and at 40 inches long it suits midsize beds as well as full-size ones.

Skip it if you carry tools longer than 40 inches or your cover hangs lower than the room left.

Most storage: Weather Guard 664 chest

The 664 is the large chest: 62 inches long, 20 deep and 19-1/4 tall, with 13.1 cubic feet and an offset-hinge lid that opens 90 degrees. The price of that size is height: it leaves 0.75 to 3.15 inches below the rail line.

“This was also the absolute largest box that would fit my 2020 Ford F-350 dually (1/2" gap left and right).”

Weather Guard 664 Aluminum All-Purpose Chest Truck Tool Box, 13.1ft³, Gloss Black (664-5-01) owner · 5 out of 5 stars

Reviews average 4.7 from 20, with one leak and one road thump reported (see care below). Another owner liked the chest but says it did not fit their truck, so check the 62 inch length against your bed floor first.

Skip it if your truck is a midsize or your cover hangs low. Our listing also says this chest does not use the 1Key UltraLock.

Budget pick: UnderCover SwingCase

The SwingCase is a molded ABS case that bolts to the inside of the bed side panel over the wheel arch. Our listing says it swings out over the tailgate and does not stand above the bed rails. It holds 1.5 cubic feet and up to 75 pounds and locks with a key. Driver and passenger sides are separate parts, listed for 13 truck lines.

Our listing says it works with most tonneau covers and names any it rules out in the part's fitment block. One owner says it fits under theirs:

“Was easy to install, fits nicely under the tonneau cover, and swings out easily with the pull of the lever.”

UnderCover SwingCase Swing-Out Truck Bed Toolbox owner · 5 out of 5 stars

Install is listed at 30 minutes or less, though a few trucks need drilling and a drop-in liner or bed rug has to be trimmed. Reviews average 4.8 from 141; one 3-star owner of both sides calls the plastic not very hard and the space small.

Skip it if you need more than 1.5 cubic feet, want a metal box or run a bed extender.

Under the bed: Weather Guard 548 underbed box

An underbed tool box solves the height problem by leaving the bed. The 548 is a welded steel box, 48 by 18 by 18 inches, with 9.1 cubic feet behind a drop-down door and a stainless compression latch.

Fit is by frame space. Our listing says the box needs about 48 inches of clear rail, 18 inches of depth and room for the door, with mounting hardware not included. It describes the 548 as a box for the frame under a flatbed, platform, service or dump body. It suits a pickup bed only where that space exists, so look under your bed before you plan on it. Our underbed range also has 24, 30 and 36 inch boxes for a shorter run of rail.

Skip it if your frame has no 48 inches of clear rail under the bed.

Wheel well box: Weather Guard 172

The 172 is a driver-side wheel well tool box: 46-5/8 by 15-3/8 inches and 16-3/8 tall, with 3.4 cubic feet and a 12V access port. It mounts over the rear wheel well with hardware included.

It rides on the wheel housing, so the bed-depth table cannot settle the fit. Measure from the bed floor to where the closed lid will sit, compare that with the lowest part of your cover and confirm the fit before ordering.

Skip it if your cover hangs low over the housing. For the passenger side, or a pair, add the matching 173.

Lo-side boxes: Weather Guard 174 and 180 sit on the rail

The 174 is a lo-side tool box about 56 inches long, 17 wide and 13 tall, with 4.0 cubic feet and a gas-strut lid. The 180 is a 41 inch Low Profile Lo-Side model with 3.0 cubic feet. Both clamp under the rail without drilling, and our listings put a clamp-on install of the 174 or 154 at about 20 to 30 minutes, easier with a second person.

Both mount on top of one bed side rail and rise above it, and a standard cover needs that same rail for its own rails and seals, so it cannot run past them. Choose a lo-side box when you will run the truck without a standard tonneau cover. The 174 averages 4.8 from 16 reviews, and the only 180 review on file warns about bed liners:

“This box did not mount easily to my f150 because I have a plastic bed liner that takes up a good portion of space between the bed and bed rail.”

Weather Guard 180 Low Profile Lo-Side Truck Tool Box, 41 in Bright Aluminum Diamond Plate (180-0-04) owner · 5 out of 5 stars

Skip it if you want a standard tonneau cover on the truck.

Crossover boxes: Weather Guard 154 and the toolbox-edition covers

The 154 is a slim midsize crossover tool box that spans the bed behind the cab: 62 by 20 inches and 13 tall, with 7.0 cubic feet, listed for the Colorado, Canyon, Ranger, Frontier and Tacoma. At $1,293 it is the most expensive box in this guide. All three reviews are 5 stars:

“Durable and well built. Size fits my 04 Tacoma perfectly!”

Weather Guard 154 Aluminum Crossover Truck Tool Box, Mid-Size Slim, Bright Aluminum (154-0-04) owner · 5 out of 5 stars

A standard cover starts where the box sits, so a crossover box needs a cover that begins behind it. The toolbox-edition covers below are listed in our range for full-size trucks only, so none pairs with the midsize 154. For a full-size truck our crossover range has full-size boxes too: the 123 is listed at 20 inches front to back, inside both covers' ranges, while the extra-wide 117 is listed at 27-1/2 inches, outside both. See also our tonneau cover with a toolbox guide.

Skip the 154 if you want a standard cover over the whole bed or drive a full-size truck.

Check how your cover opens

Where the cover goes when it opens matters as much as height. Most standard covers open toward the cab: a soft folding cover such as the Extang Trifecta 2.0 folds forward, a roll-up such as the Access Original rolls up at the front and a retractable such as the RetraxPRO MX stores in a canister at the cab end. Our chest listings describe pushing the chest tight against the front of the bed, the same end, so open your cover fully with the box in place and check that the lid still lifts. Our guide to types of truck bed covers shows each style.

Locks and warranty

Each box keeps its own lock. The 1Key UltraLock lets one key open several Weather Guard boxes. The SwingCase has its own key lock and, per our listing, 1 year on the ABS structure and 1 year on the lock, hinges and hardware. With a folding, roll-up or retractable cover the bed is only as secure as the tailgate lock, as our guide to tonneau covers with locks explains. Weather Guard's own truck FAQ lists a limited lifetime warranty on its truck boxes against manufacturer defects, with the terms in the manual.

Care and lifespan

Check the mounting bolts and clamps after the first few drives: one 664 owner traced a road thump to the box moving slightly on its four bolts. Look inside after heavy rain, because the 2-star 664 owner lost a tool bag to mold from a driver-side leak. The limited lifetime warranty above covers manufacturer defects, so report a leak or a failed latch early.

Frequently asked questions

Can you put a tool box under a tonneau cover?

Yes, when the box stays below the cover. A chest or wheel well box works if its closed lid clears the cover's underside, the SwingCase is listed for most covers and an underbed box works with any cover if your frame has room for it. Rail-mounted lo-side and crossover boxes do not fit under a standard cover.

How do I know if a tool box will fit under my cover?

Subtract the box height from your bed depth. If the room left is larger than how far your cover hangs below the rail line, the lid clears.

Will a wheel well tool box fit under a tonneau cover?

It can, but bed depth does not settle it because the box rides on the wheel housing. Measure from the bed floor to where the closed lid will sit and compare that with your cover.

Does a lo-side tool box work with a tonneau cover?

Not with a standard one. Our lo-side boxes mount on top of one bed side rail and rise above it, where a standard cover's rails and seals need to sit.

Can I use a crossover tool box with a tonneau cover?

Only with a toolbox-edition cover, which starts behind the box. Our toolbox editions are listed for full-size trucks, so pair one with a full-size crossover such as the 123, which our listing gives as 20 inches front to back, inside both covers' listed ranges. The midsize 154 has no toolbox edition in our range. Check the cover's listed box depth on its part page.

Will my tools stay dry under a cover?

The Weather Guard boxes list weather seals, so each box protects its own contents. The SwingCase lid closes onto a weathertight seal, though no waterproof rating is published. Covers differ in how well they seal, which our guide to waterproof tonneau covers compares. One 664 owner reports a leak.

Related guides

• Tonneau Cover With a Toolbox: Which Covers Work Over or Around a Box
• How to Measure Your Truck Bed for a Tonneau Cover (With Bed Size Chart)
• Types of Truck Bed Covers: Every Tonneau Style Compared