The 6 Best Tool Boxes for Under a Tonneau Cover of 2026

The TonneauMate is the most expensive box we recommend here, and the only one that behaves like part of the truck rather than a crate set inside it. Ten cubic feet and a 200-pound capacity is roughly five times what the SwingCase holds, and the box hangs suspended from the bed rails so lumber and sheet goods still slide underneath.

That suspension is why we kept it on the list after the first look at the price. Most chests eat the front of a covered bed and make you climb in after them; this one puts the storage up in the airspace a tonneau already creates, and the multiple mounting positions let you shift it fore or aft as your load changes. The composite body won't dent or corrode the way tread-plate aluminum does, and it carries a two-year warranty.

The brackets are the part to watch. They clamp rather than screw into the bed, which is exactly what makes the box removable, and they're the item that arrives needing attention — check the torque at installation and again after the first long drive with a load. It also opens from the driver side only, which is fine working from the tailgate and awkward from the curb.

Fit is the other thing to settle before you order. It takes most full-size beds but not Flareside, Stepide, or composite beds, and there's no adapter that changes that. Where it does fit, the lock keeps the lid shut and the under-cover position keeps the whole box out of sight, which matters more than the lock in a truck that sits in a lot all day.

Two boxes for roughly the money of one SwingCase is the argument, and OEDRO makes it well: the kit ships with a driver-side and a passenger-side box, each of which rotates 180 degrees toward the tailgate the same way the UnderCover does.

The pair makes more sense than a single box on a covered truck, because the shallow wells over the wheel arches are dead space in every bed. At about 35 by 16 by 10 inches each they take up less room than a cross-bed chest, the molded plastic won't rust or dent, and a closed cover hides them completely. What we appreciated most is the removable tray — lift it out and you have a parts bin for the job at hand instead of a bucket to dig through.

The mounting is the part that gives us pause. It uses straps and bolts rather than screws into the bed, which means more adjustment during installation and a deliberate check after the first week of driving. The boxes do stay put once the straps are tensioned, but it's a mounting you verify rather than glance at. Fit is limited to the 2015-2021 F-150, so confirm your model year before you order.

Seven inches of height is the entire case for this box, and under a tonneau cover it's a strong one. Roll-up and retractable covers give up bed space to a canister at the bulkhead and leave only a shallow opening over the floor; a chest standing 15 inches tall spends its life fouling the rails, while this one slides underneath with room to spare. At 35 by 13 by 7 inches and under 14 pounds, one person can lift it out and set it on the tailgate.

It's aluminum, powdercoated black with a five-bar tread, and the overlapping lid is shaped to shed water rather than pool it. There's a keyed latch with two keys, which is the whole of the security — leave the cover off in a lot and a determined person with a screwdriver wins. The gauge is light, so it's happiest carrying straps, hand tools, and a hitch receiver rather than a load of firewood bouncing on top of it.

The size turns out to be the useful part. It slots between the wheel wells of a short bed, bolts to a hitch rack or an enclosed trailer tongue, and disappears into the back of a side-by-side when the truck stays home. Three feet of light aluminum isn't a load-bearing surface, but as a lockable, liftable place for gear you want out of sight, it earns its spot — especially in the trucks where nothing taller will close.

Forty-nine inches long and fifteen inches tall makes the ARKSEN a chest, not a nook filler. Under a tonneau cover it occupies most of the width of the bed at the front or the tailgate, and the lid swings up into whatever clearance the cover leaves you — which is the thing to picture before you buy.

Where it earns its keep is as a sealed general-purpose box. The diamond-plate body has side handles, a keyed latch, and a claimed waterproof, dustproof interior, and 180 liters swallows gas cans, trimmer line, tie-downs, kindling, or a camper battery. At 26 pounds it's light enough to move between a trailer tongue and a truck bed, which is how a lot of these actually get used.

We rate it as a trailer and front-of-bed chest that happens to fit under a cover, not a purpose-built under-cover solution. The lid has no prop or strut, so you hold it up with one hand while you dig with the other — worse in a covered bed, where you can't stand it upright. The latch takes some fiddling to catch, and the welds and finish vary enough that it wants a look-over before it goes on a trailer tongue. As a big, cheap, lockable box that stays put and gets opened a few times a week, it does the job.

Two lockable front latches, welded corners, and lift arms that hold the lid at an angle: from the outside the confote looks like a chest costing considerably more. What sets the price is the part you can't see.

The aluminum is thin. Thirty-nine inches of box at around twenty pounds tells you most of what you need to know before you open the carton, and the first months of use bear it out — a knock in a parking lot leaves a dent, and the side handles and latch hardware can start to show rust before the body does. Treat it as a light-duty, fair-weather box and it holds up fine; treat it as a fixture that lives outdoors and it won't.

Under a tonneau cover the math shifts in its favor. A covered box isn't sitting in the rain or taking sun, and what's left is a cheap, light, lockable aluminum chest that swallows straps, jumper cables, a come-along, and a quart of oil without complaint. One number to know: the 39 by 13 by 10 figures are outside dimensions. The walls and the latch hardware eat into that, so measure the inside if a particular tool case has to fit.