The U.S. truck bed accessories market — the category that includes tonneau covers, bedliners, storage systems, and toolboxes — was valued at roughly $2.72 billion in 2025 and is projected to reach $3.83 billion by 2030, a 7.1% CAGR, according to Grand View Research. Storage systems and toolboxes sit inside that broader category alongside tonneau covers, and the two products increasingly have to coexist on the same bed rather than compete for it. That’s the entire reason a side tool box exists: instead of spanning the full width of the bed like a crossover box, it clamps to a single side rail and runs lengthwise along it, leaving the floor, the opposite rail, and almost the entire length of the bed open for cargo, a tonneau cover, or both at once.
Key Takeaways
- A side tool box mounts to one bed rail and runs front-to-back along it, unlike a crossover box, which spans the full width of the bed just behind the cab.
- Because it occupies only one rail, a side box preserves nearly the full usable floor length of the bed for long cargo — lumber, ladders, ATVs — that a crossover box’s front-mounted footprint would otherwise block.
- Low-profile side boxes (typically 9-12 inches tall) are built specifically to clear the underside of a roll-up or folding tonneau cover, something a taller crossover box usually can’t do without leaving a gap or forcing the cover to stop short.
- Boxes can be run single (one rail) or paired (matching boxes on both rails), and a paired setup roughly doubles both capacity and price while still leaving the center of the bed floor open.
- Expect to pay $190-$500 per box depending on material, length, and lid hardware; paired setups on a full-size long bed sit at the top of that range.
Side-Mount vs. Crossover: Two Different Ways to Store Tools
The fundamental difference between a side tool box and a crossover tool box comes down to which axis of the bed each one occupies. A crossover box sits across the width of the bed, typically wedged against the front bulkhead just behind the cab, spanning from one side rail to the other. That gives it a large, deep, single compartment, but it also eats 18-20 inches of bed length in a single continuous block, and it sits at the very front where a tonneau cover’s front rail usually has to stop or work around it. A side tool box takes the opposite approach: it clamps to one bed rail and runs parallel to it, front to back, occupying a narrow strip along the edge of the bed rather than a wide block across it. The floor underneath stays open, the opposite rail stays completely bare, and the box can run nearly the full length of the bed without ever touching the center of the cargo area.
That difference matters most for two groups of buyers: people who regularly haul long, bulky items that need the full floor length of the bed — sheet goods, ladders, pipe, ATVs on a ramp — and people who run a tonneau cover and don’t want a tall crossover box interrupting the cover’s seal or forcing an awkward step in its profile. A side box’s low, narrow shape was built around exactly that second problem. Most low-profile side boxes top out around 9-12 inches in height, low enough to sit underneath a roll-up or folding soft cover with the cover simply draping over the top, rather than needing a cutout or a raised section the way a taller crossover box often does.
Low-Profile Height and Tonneau Clearance
Height is the single spec that determines whether a side box will work with a given tonneau cover, and it’s worth checking before anything else. Standard-depth crossover boxes commonly run 16-19 inches tall, which is too tall for most roll-up or folding covers to clear without a step or a gap at the front. Low-profile side boxes are purpose-built to stay under that ceiling, usually landing between 9 and 12 inches, specifically so a soft cover can roll or fold directly over the top of the box without interruption. Hard tri-fold and hard roll-up covers are less forgiving on this point than soft roll-ups, since their rigid panels need a flat, continuous surface to seal against — always check a specific cover manufacturer’s clearance spec against the box’s exact height rather than assuming “low profile” alone guarantees a fit.
Single Side Box vs. a Matched Pair
Most buyers start with a single box on the passenger side, which is enough storage for a typical set of hand tools, tie-downs, and recovery gear while leaving the driver’s side rail and the entire floor open. Contractors and buyers who need more dedicated storage often step up to a matched pair — one box on each rail, usually the same brand and length so the lids line up — which roughly doubles both capacity and cost but still leaves the center of the bed floor completely clear for cargo, unlike adding a second crossover box would. A paired setup is really the closest a side-mount system gets to a crossover box’s total volume, just distributed along both edges instead of stacked across the front.
The Best Side Tool Boxes Worth Buying
1. UWS TBS-69-LP-BLK Low Profile Single Lid Side-Mount Box
UWS’s low-profile side series is purpose-built around the tonneau-clearance problem: it uses a slim gas-strut lid and a shallow-well design that keeps overall height low enough to sit under most roll-up covers without a gap. The 69-inch length is sized to run nearly the full length of a standard short or long bed rail depending on cab configuration. Approximate price: $260-$300.
Best for: buyers running a soft roll-up tonneau cover who need the shallowest possible clearance under it.
2. WEATHER GUARD Lo-Side Box (Model 121-3-02)
Weather Guard’s Lo-Side line takes the same 18-gauge steel and textured black powder coat construction that makes their saddle boxes a fleet-truck staple and reshapes it into a narrow, rail-mounted profile. It’s rated for the same daily-abuse duty cycle as their crossover models, just distributed along one rail instead of across the bed. Approximate price: $290-$330.
Best for: contractors and fleet trucks that need a narrow steel box rated for genuine daily jobsite abuse.
3. Brute Contractor Topsider Low Profile Side Mount Tool Box
The Brute Topsider is one of the longest single-rail boxes commonly available, built to run the full length of a long-bed rail rather than a shorter fixed segment. Its low-profile lid and full-length piano hinge are designed specifically to maximize length without adding height, which keeps the box out of the way of a tonneau cover running over the rest of the bed. Approximate price: $340-$390.
Best for: contractors who want maximum length along one rail without touching the opposite side of the bed at all.
4. Dee Zee Specialty Series Slim-Line Side Box (DZ8536)
Dee Zee’s Slim-Line side box uses the same diamond tread aluminum and stainless paddle handle as their Red Label crossover line, scaled down to a narrower rail-mount footprint. It’s sized specifically for mid-size trucks, where a full-width crossover box would eat a disproportionate share of an already-shorter bed. Approximate price: $230-$270.
Best for: mid-size trucks (Ranger, Tacoma, Colorado-class) where every inch of the opposite rail and the floor matters.
5. Better Built SEC Series Slim-Line Side Box
Better Built’s SEC Series is the budget entry point into real aluminum side-mount storage, using a single-point paddle latch and manual lid to keep the price well below the premium brands above it. Build gauge is noticeably lighter than the Weather Guard or Brute options, but for occasional tool and gear storage rather than daily jobsite duty, it’s a reasonable trade for the price. Approximate price: $190-$230.
Best for: budget-conscious buyers who want genuine aluminum construction without commercial-duty pricing.
6. Highway Products Diamond Tread Aluminum Side Box
Highway Products builds its side boxes to custom lengths rather than a handful of fixed sizes, which matters if your bed length falls between the standard 48-, 60-, and 69-inch options most competitors offer. The tradeoff for that fit precision is a longer lead time and a price premium over an off-the-shelf box of similar capacity. Approximate price: $400-$500.
Best for: buyers who want a box built to their bed’s exact length rather than a fixed off-the-shelf size.
7. Buyers Products 1712315 Slimline Aluminum Side Mount Box
Buyers Products carries the same no-frills, work-truck-first approach to its side boxes that defines its crossover line: diamond tread aluminum, a t-handle compression latch instead of a paddle handle, and pricing aimed at fleet buyers stocking multiple trucks rather than a single retail purchase. Approximate price: $220-$260.
Best for: fleet buyers equipping multiple trucks who want simple, durable hardware at a lower unit cost.
Capacity Comparison
Price Comparison
Spec Comparison at a Glance
| Model | Material | Height | Capacity | Approx. Price |
|---|---|---|---|---|
| UWS TBS-69-LP-BLK | Aluminum diamond plate | Low profile (~10 in) | 4.8 cu ft | $260-$300 |
| WEATHER GUARD Lo-Side 121-3-02 | 18-gauge steel | Low profile (~11 in) | 4.2 cu ft | $290-$330 |
| Brute Contractor Topsider | Aluminum diamond plate | Low profile (~12 in) | 5.6 cu ft | $340-$390 |
| Dee Zee Slim-Line DZ8536 | Aluminum diamond tread | Low profile (~10 in) | 3.6 cu ft | $230-$270 |
| Better Built SEC Series | Aluminum diamond plate | Low profile (~9 in) | 3.4 cu ft | $190-$230 |
| Highway Products Custom | Aluminum diamond tread | Low profile (custom) | 5.0 cu ft | $400-$500 |
| Buyers Products 1712315 | Aluminum diamond tread | Low profile (~10 in) | 3.8 cu ft | $220-$260 |
Frequently Asked Questions
Will a side tool box fit under my tonneau cover?
Usually, if the box is genuinely low-profile and your cover is a soft roll-up or folding style, since those covers simply drape over whatever is underneath as long as there’s no obstruction taller than the cover’s own clearance. Hard tri-fold and hard roll-up covers are stricter, since their rigid panels need a continuous, mostly flat surface to close and seal against. Always check the box’s exact height against the cover manufacturer’s clearance spec before ordering either product.
Should I get one side box or a matched pair?
A single box on the passenger side covers most owners’ needs — hand tools, straps, recovery gear — while leaving the driver’s rail and the whole floor open. Step up to a pair only if you genuinely need more dedicated, lockable storage than one box provides; a pair roughly doubles cost and capacity but still leaves the bed floor’s center completely clear, which a second crossover box would not.
How much bed length does a side box actually leave usable?
Far more than a crossover box in absolute terms, since a side box occupies a narrow strip along one edge rather than a full-width block across the bed. The tradeoff is that a side box’s floor footprint isn’t zero — its width (typically 10-14 inches) still narrows the usable floor on that side, so very wide cargo laid flat across the full bed width may need to shift toward the open rail.
Do side boxes require drilling into the bed?
Most current side boxes clamp to the bed rail or bed cap with bracket hardware, the same no-drill approach used by most crossover boxes, so no factory bed liner warranty is affected. A handful of older or custom-length models use bolt-through mounting into the rail, so confirm the mounting method before ordering if a no-drill install is a requirement.
Aluminum or steel for a side box specifically?
The same tradeoff applies as with crossover boxes: aluminum won’t rust and weighs less, which matters more on a narrow box mounted at the very edge of the bed where any added weight sits furthest from the truck’s centerline. Steel resists dents and impact better and costs less, but needs its powder coat finish to stay intact to avoid corrosion, especially in road-salt climates.
The Bottom Line
A side tool box solves a different problem than a crossover box solves. If you need maximum storage volume in the smallest number of mounting points and don’t mind losing 18-20 inches of bed length up front, a crossover box is still the more space-efficient single purchase — need maximum storage volume instead of preserving bed length? see our guide to the best crossover tool boxes. But if you regularly haul long cargo that needs the full floor length, or you run a tonneau cover and don’t want a tall box interrupting its profile, a low-profile side-mount box built to clear that cover and hug one rail is the better fit. Start with a single box on the passenger side if you’re not sure how much storage you actually need, confirm its height against your tonneau cover’s clearance spec before you order either product, and step up to a matched pair only once one box genuinely isn’t enough.
