Best Side Boxes For Flatbed: Compare 10 Storage Designs

#1 · Best Overall

1. Mytee Products Flatbed Box

• Dimensions: 20"L x 20"W x 20"H
• Weight: 100 lb
• Material: Aluminum

Best for: Heavy-duty trailer underbody storage.

Why it ranks #1: Explicitly intended for flatbeds, platforms, step decks and dump bodies; it pairs a 60-inch aluminum body with double barn doors and a paddle lock.

A double barn-door opening with a heavy-duty paddle lock gives this Mytee Products aluminum box wide, secured access for flatbed and semi-truck storage. The description lists a 60 × 24 × 24-inch body with 11-gauge-equivalent, 3 mm material, waterproof hinges, and stainless-steel handles for its side-mount trailer application.

The stated 60-inch length and 24-inch height and depth provide a large compartment for tools and equipment on a flatbed, platform, step deck, or dump-truck body. Double barn doors open the compartment, while the paddle lock supplies the listed locking method. Aluminum is described as lightweight and rust-resistant; waterproof hinges and stainless-steel handles address exposed hardware. Specifications list a 440-pound capacity, but another dimension entry shows 20 × 20 × 20 inches, so resolve that discrepancy for placement.

Skip it if you need consistent dimensions for installation planning; Buyers Products 1721551 lists the same 72 × 13 × 16-inch dimensions in its title and specifications.

Consider this for flatbed, platform, step-deck, or dump-truck owners wanting a large aluminum compartment with barn doors and a paddle lock. Verify the conflicting listed dimensions before planning its mounting location.

Listed on Amazon as: Mytee Products 24"x24"x60" Aluminum Flatbed Trailer Underbody Tool Box with Barndoor Style Double Door & Paddle Lock – Heavy Duty Side Mount Tool Box for Trailer & Semi Truck

#2 · Longest Side Box

2. RKI Upper Side Box

• Weight: 287 lb

Best for: Welding-truck divider storage.

Why it ranks #2: The listing identifies flatbeds as a use case, and its 96-inch steel upper-side box includes a top-opening compartment and eight dividers.

Eight included dividers and adjustable slots on 2-inch centers make the RKI 96-inch upper side box configurable for separating equipment. Its 4.5-inch-deep top-opening compartment adds shallow, organized storage, while the 14-gauge cold-rolled steel construction and stated suitability for welding trucks, flatbeds, and equipment trailers target work-vehicle use.

At 96 inches long, this upper-side box suits applications with room for an extended cabinet, including flatbeds and equipment trailers. The top-opening compartment is 4.5 inches deep, and its adjustable slots on 2-inch centers let users arrange the eight included dividers around smaller items. The 14-gauge cold-rolled steel construction provides a specified material and gauge for evaluating the cabinet. Its listed product dimensions are 97.5 × 21 × 16.5 inches, relevant to installation planning.

Skip it if you need a lightweight aluminum box; Buyers Products 1721551 is an aluminum topsider listed at 78 pounds.

This suits welding-truck, flatbed, or equipment-trailer operators needing a long upper-side cabinet and adjustable small-item dividers. The 287-pound listed weight and 97.5-inch package dimensions require suitable handling and installation planning.

Listed on Amazon as: RKI UST96CB Black 96" Steel Top-Opening Upper Side Truck Box

#3 · Mounting Kit Included

3. Fsehyue Saddle Step Box

• Dimensions: 15"L x 28"W x 25"H
• Material: Aluminum

Best for: Flatbed trailer saddle-step storage.

Why it ranks #3: Described for flatbed trailers and semi trucks, this aluminum saddle step box includes two 24-inch mounting brackets and two keys.

Included 24-inch mounting brackets pair this 15 × 28 × 25-inch Fsehyue aluminum saddle-step box with flatbed trailer and semi-truck use. Its T-shaped handle lock and two included keys provide lockable access, while the reinforced aluminum body is described as windproof and rainproof for protecting stored tools in harsh weather.

The 28-inch width and 25-inch height create a substantial side-storage compartment, and the saddle-step format targets semi trucks and flatbed trailers. Included 24-inch mounting brackets support its intended mounting setup, while the T-shaped handle lock and two keys give the owner a lockable closure. The listing describes the aluminum as reinforced and the box as airtight, with weatherproof protection intended to reduce exposure of stored tools to rain and wind.

Skip it if you need a shallower 13-inch-high rail-side cabinet; Weather Guard's 56-inch Lo-Side box is listed at that height.

This is a fit for semi-truck or flatbed-trailer owners seeking a tall, lockable saddle-step compartment with brackets included. Its 25-inch height makes available vertical clearance an important installation consideration.

Listed on Amazon as: 15"x28"x25" Aluminum Side Storage Saddle Step Box Heavy Duty Semi Truck Toolbox with Lock and Keys Weatherproof Storage Organizer with 24" Mounting Brackets Suitable for Semi Trucks Flatbed Trailer

#4 · Dual-Door Access

4. Buyers Products Topsider Box

• Dimensions: 72"L x 13"W x 16"H
• Weight: 78 lb
• Material: Aluminum

Best for: Long-bed rail-side tool storage.

Why it ranks #4: Its 72-inch rail-mounted aluminum cabinet has two drop doors and 8.67 cubic feet of capacity for accessible work-truck tool storage.

Two recessed drop doors span this 72-inch Buyers Products topsider, giving workers access to tools along the cabinet without reaching over its full length. Its .100-inch diamond-tread aluminum construction combines a stated lightweight build with corrosion resistance, while the rail-mounted format keeps storage within reach and preserves truck-bed space.

The 72 × 13 × 16-inch profile and 8.67-cubic-foot capacity suit long tools and jobsite supplies, while mounting to bed rails keeps them accessible without occupying the bed floor. Two recessed drop doors allow access at separate points along the cabinet, and continuous hidden hinges with aircraft-grade support cables support everyday opening and closing. Aluminum construction and a black powder-coated finish provide corrosion resistance; its 78-pound listed weight is relevant when planning installation.

Skip it if you need a deep underbody compartment; EASYBERG's 36-inch box measures 18 inches wide and 18 inches high.

Choose this for a work truck needing long, rail-mounted storage with two access points and corrosion-resistant aluminum. Its 13-inch width and 16-inch height set a shallow profile, so check that your gear suits those dimensions.

Listed on Amazon as: Buyers Products 1721551 72 x 13 x 16 Inch Black Aluminum Topsider Box

#5

5. VEVOR Contractor Box

• Dimensions: 72.05"L x 12.99"W x 15.94"H
• Weight: 45.2 lb
• Material: Aluminum, Stainless Steel

Best for: Long-tool dual-compartment storage.

Why it ranks #5: This 72-inch aluminum topsider has dual drop doors and two large compartments, offering long-tool storage for buyers whose flatbed rails suit its dimensions.

Two large compartments and dual drop doors give this 72-inch VEVOR topsider separated storage with access along a long bed-rail cabinet. Its 0.07-inch aluminum construction, welded structure, and fixed rods are specified to resist wear, hold shape, and stay in place on bumpy roads, while the listed dimensions are 72.05 × 12.99 × 15.94 inches.

The long, narrow profile accommodates power drills, cables, pipe wrenches, and crowbars according to the supplied description, while two compartments help organize gear and reduce rattling. Dual drop doors provide access without opening a single full-length lid. A two-position latch gives a specific closure feature, and the included fixed rods and J-hooks support securing the box. Its 45.2-pound listed weight and aluminum construction are useful considerations when planning placement and handling.

Skip it if you need 8.67 cubic feet in a 72-inch cabinet; Buyers Products 1721551 lists that capacity in a similar topsider format.

Choose this for long tools and a divided, rail-top storage workflow, especially when the included rods and J-hooks are useful. Its roughly 13-inch width is a meaningful limit for bulky gear needing more depth.

Listed on Amazon as: VEVOR Contractor Truck Tool Box, 72 x 13 x 16 in, With Dual Drop Doors

#6

6. FGJQEFG Side Mount Pair

• Dimensions: 61.81"L x 16.54"W x 15.16"H
• Weight: 84 lb
• Material: Aluminum

Best for: Two-piece side storage set.

Why it ranks #6: The black aluminum two-piece set is listed for truck, RV and trailer storage, with a 60-inch nominal size and lock-and-key access.

This FGJQEFG listing supplies two side-mount aluminum toolboxes, offering paired storage for pickup beds, RVs, or trailers. Each box is titled as 60 × 8 × 14 inches, with a weather-resistant overlapping lid and seal-ring design described to help keep rainwater and other contaminants out of the storage area.

The two-piece configuration can separate tools or supplies between side positions, while the side-mount format keeps the boxes oriented for truck-bed or trailer storage. The listed dimensions are 61.81 × 16.54 × 15.16 inches, and the title separately gives 60 × 8 × 14 inches, so those measurements differ and merit attention during space planning. Aluminum construction is described as lightweight and corrosion-resistant; the overlapping lid and seal ring support weather protection.

Skip it if you need one clearly specified long topsider; VEVOR's 72-inch dual-drop-door box has matching listed dimensions in its title and specifications.

This set fits buyers seeking paired side storage for a pickup, RV, or trailer and value the stated weather-sealing details. Compare the conflicting title and specification dimensions against available mounting space before choosing it.

Listed on Amazon as: 60'' Inch Aluminum Side Mount Truck Tool Box Pick Up Truck Bed RV Trailer Toolbox Storage Organizer with Side Handle, Lock & Keys,Black,5 Bar Tread (60"X8"X14")-2PCS

#7

7. higehio Alloy Steel Pair

• Dimensions: 34"L x 12.2"W x 15"H
• Material: Alloy Steel

Best for: Balanced dual-side bed storage.

Why it ranks #7: Its two alloy-steel boxes mount along both bed rails and leave the center floor open, but the listing focuses on pickup or trailer compatibility.

A symmetrical two-box layout mounts along both bed rails, keeping the center floor open for larger cargo while providing access from either side. The higehio alloy-steel boxes measure 34 × 12.2 × 15 inches, and their dual gas struts lift the lids smoothly and hold them open for retrieval.

The paired side-facing boxes distribute storage across both bed rails, making tools accessible from either side without climbing onto the bed and preserving the center for bulky loads. Each 34 × 12.2 × 15-inch compartment gives a defined footprint for space planning. Heavy-duty alloy steel with black powder coating supplies the listed protective finish, while dual gas struts support hands-free lid access. The lockable feature adds a closure option for stored tools.

Skip it if you need longer individual side boxes; Vigorighter's two-pack lists 36.8-inch boxes with direct side access.

Pick this for buyers wanting balanced access from both sides and an open center bed floor for larger cargo. Its 34-inch box length and 12.2-inch width define the available storage footprint.

Listed on Amazon as: 2-Pack Alloy Steel Side Mount Truck Box, 34"x12.2"x15", Black

#8

8. Weather Guard Lo-Side Box

• Dimensions: 56"L x 17"W x 13"H
• Weight: 50 lb
• Material: Aluminum

Best for: Full-size pickup lo-side storage.

Why it ranks #8: The 56-inch aluminum box offers lockable storage and a limited lifetime warranty, but its verified fit description specifies full-size pickups with eight-foot beds.

Weather Guard lists this 56-inch Lo-Side box as fitting full-size pickups with 8-foot beds, giving owners a defined bed-length compatibility target. Its improved high-security locking system addresses tool security, while the aluminum cabinet measures 56 × 17 × 13 inches and holds four cubic feet for keeping important tools and accessories handy.

The 56-inch length and 17-inch width provide a low-side storage format for tools, materials, and accessories, with a 13-inch height keeping the stated profile compact. Its four-cubic-foot capacity makes the storage limit clear when deciding what to carry. The improved high-security locking system adds a security feature, and the aluminum construction is paired with a lockable, rust-resistant specification. Weather Guard says Lo-Side boxes can be used alone or with Cross or Saddle boxes.

Skip it if you need 8.67 cubic feet of rail-top storage; Buyers Products 1721551 lists more than twice this box's capacity.

Consider this for a full-size pickup with an 8-foot bed when a lockable, low-side aluminum box is the goal. Its four-cubic-foot capacity is the key boundary for larger tool collections or bulky gear.

Listed on Amazon as: Model 174-5-04 56in Lo-Side Box, Aluminum, Gloss Black, 4.0 cu ft

#9

9. EASYBERG Underbody Box

• Dimensions: 36"L x 18"W x 18"H
• Weight: 40.1 lb
• Material: Aluminum

Best for: Compact underbody gear storage.

Why it ranks #9: This 36-inch aluminum underbody box has double barn doors and a rubber seal, but its underbody format is less directly suited to side-rail storage.

A double barn door gives this 36-inch EASYBERG underbody box wide access to its 6.75 cubic feet of storage, making tools easier to reach from a lower mounting position. The aluminum cabinet measures 36 × 18 × 18 inches and includes a rubber seal, combining compact storage dimensions with stated corrosion resistance for truck or trailer use.

Its 18-inch width and height create a substantial compartment within a 36-inch length, and the underbody placement uses space beneath the bed rather than cargo-floor area. Double barn doors provide broad access to power tools and jobsite gear, while the rubber seal supports protection from moisture. Aluminum construction is listed as corrosion-resistant, and the box weighs 40.1 pounds, a useful figure for planning handling and mounting.

Skip it if you need a 72-inch rail-top cabinet; Buyers Products 1721551 provides that length and dual drop-door access.

This suits truck or trailer owners seeking an underbody compartment for power tools and jobsite essentials, with barn-door access and a rubber seal. Its 36-inch length is the boundary if your equipment needs a longer cabinet.

Listed on Amazon as: 36" Aluminum Underbody Truck Tool Box with Cam Lock, Double Barn Door

#10

10. Vigorighter Side Mount Boxes

• Dimensions: 36.8"L x 12"W x 12.5"H
• Material: Alloy Steel

Best for: Steel side-rail two-box setup.

Why it ranks #10: The two steel boxes provide side access and preserve bed space, but their stated use is a pickup truck rather than a flatbed truck or trailer.

The two-box pack mounts along truck-bed side rails, providing direct side access while leaving more of the cargo bed available. Each Vigorighter steel box measures 36.8 × 12 × 12.5 inches and has a lock latch with keys; the powder-coated, corrosion-resistant alloy-steel construction is specified for tool and gear storage.

With two boxes, the setup can keep tools or camping supplies in separate side positions, and the stated side access lets users retrieve items without climbing into the bed. Rail mounting preserves bed space for cargo, planks, or other loads. Each 36.8-inch-long box has a 12-inch width and 12.5-inch height, defining a relatively slim storage profile. Powder coating and corrosion-resistant alloy steel support durability, while the lock latch and keys add secured closure.

Skip it if you need wider, deeper storage; Fsehyue's saddle-step box measures 28 inches wide and 25 inches high.

This set suits pickup owners who want two lockable side-rail compartments for tools or camping gear while keeping the bed center open. The 12-inch width and 12.5-inch height limit what each box can hold.

Listed on Amazon as: 36 Inch Side Mount Tool Box 2 Pack, 36.8 x 12 x 12.5 Inch Steel Pickup Truck Side Tool Box Storage ToolBox with Lock Latch and Keys, Black (Pack of 2)