Side Mount Truck Tool Boxes

Shop side mount truck tool boxes from Upfit Supply — low-profile aluminum and steel storage that mounts along your truck bed rail, keeping the center of your bed completely open for hauling pipe, lumber, ladders, and long materials. Also called lo-side boxes, low-side tool boxes, or rail boxes, these are the go-to solution for contractors who need secure, lockable tool storage without sacrificing bed space. We carry Weather Guard, UWS, Dee Zee, and Brute — free shipping on most boxes, 1-2 business day fulfillment from our nationwide network of warehouses. Use the vehicle filter to confirm fitment, or browse by brand below.

What Are Side Mount Truck Tool Boxes?

Side mount tool boxes mount along one or both bed rails at a low profile — unlike a crossover box, which spans the full width of the bed behind the cab. This leaves the center of your truck bed completely accessible from above and from the tailgate, making side mount boxes the right choice when you need both tool storage and the ability to carry long materials in the same trip. Most clamp directly to the bed rail without drilling, making them easy to install and removable at lease end.

Types of Side Mount Truck Tool Boxes

Lo-Side Tool Boxes

The most common style — a low-profile rectangular box that mounts along the bed rail on one or both sides. Keeps the box below the rail line, reducing wind resistance and keeping the full bed width accessible from above. Available in single-side and dual-side configurations. Popular with plumbers, electricians, and contractors who regularly carry pipe, conduit, or long lumber in the bed.

Low Profile Side Mount Boxes

An extra-slim height that sits entirely below the bed rail level — nearly invisible from outside the truck. Particularly useful on crew cab trucks with shorter 5.5 ft beds where clearance is limited, or for contractors who want a clean look without sacrificing storage.

Side Mount Tool Box Brands

Weather Guard Lo-Side Boxes

Heavy-gauge steel construction with ARMOR TUF powder coat finish — the same commercial standard as Weather Guard's crossover lineup. Dual-action rotary locking and a limited lifetime warranty. The right choice for fleet standardization and contractors who demand long-term durability. Available in standard and low-profile heights.

UWS Side Mount Boxes

Aluminum lo-side boxes with a patented ratcheting lid and bright mill finish. Significantly lighter than steel — important if you're running a half-ton truck close to its payload limit. A competitive price point makes UWS the most popular aluminum lo-side option for contractors who want lightweight storage without the premium price.

Brute Lo-Side Boxes

Heavy-duty steel at a lower price point than Weather Guard. Straightforward commercial-grade construction for contractors who prioritize durability and value without needing a lifetime warranty or premium finish.

Dee Zee Side Mount Boxes

High quality steel and aluminum options from a well-known truck equipment manufacturer.

Side Mount vs. Crossover: Which Is Right for You?

• Choose a side mount / lo-side box if: You carry pipe, conduit, lumber, rebar, or other long materials in the bed regularly. You want tool storage without blocking overhead bed access. You prefer a lower profile.
• Choose a crossover box if: Maximum interior storage volume is your priority and you don't regularly haul long materials in the bed.
• Run both if: Many contractors combine a crossover box behind the cab with lo-side boxes along the rails — maximum storage volume plus side-accessible tool storage, with the rear of the bed still open for materials. Confirm bed length compatibility before running both.

Who Uses Side Mount Truck Tool Boxes

• Electricians — Store wire, fittings, and hand tools in lo-side boxes on both rails while carrying conduit and wire spools flat in the center of the bed.
• Plumbers — Keep tools organized and accessible on the sides while pipe and fittings ride in the open center.
• HVAC Technicians — Side-access storage on both rails while the bed stays clear for equipment and materials.
• Contractors & Carpenters — Carry lumber and long stock in the open bed while keeping hand tools, fasteners, and smaller power tools secure from the side.
• Landscapers — Tool storage on the rail with the bed clear for equipment, soil, or plant material.

Related Truck Tool Box Types

• Crossover / Saddle Boxes — Full-width storage spanning both bed rails. Maximum storage volume.
• Top Mount Boxes — Higher-profile rail-top storage with more interior depth.
• Underbody Boxes — Mounts beneath the truck frame. Keeps the bed entirely clear.
• All Truck Tool Boxes — Browse the full selection across all styles and brands.

Side Mount Truck Tool Box FAQs

What is a side mount truck tool box?

A side mount truck tool box mounts along one or both bed rails at a low profile, keeping the center of the truck bed completely open for hauling long materials. Also called a lo-side box or low-side box, it gives you secure lockable storage without sacrificing bed access from above or from the tailgate.

What is the difference between a side mount box and a crossover box?

A crossover box spans the full bed width on top of both rails — maximum storage, but it covers the front of the bed. A side mount or lo-side box mounts along one or both rails at low profile, keeping the center of the bed open. If you regularly carry pipe, lumber, or long materials, a side mount box is the better fit.

What is a lo-side tool box?

Lo-side is another name for a side mount truck tool box — a low-profile box that mounts along the bed rail. Available in single-side and dual-side configurations from Weather Guard, UWS, and Brute. All ship free from Upfit Supply.

Do side mount tool boxes require drilling?

Most lo-side truck tool boxes clamp to the bed rail with J-bolts or rail clamps — no drilling required. This makes them easy to install, fully removable, and safe for leased trucks. Some configurations may require drilling — always confirm the installation method in the product listing before purchasing.

Can I use a side mount box and a crossover box together?

Yes — combining a crossover box behind the cab with lo-side boxes on both rails is a common contractor setup. The crossover handles large-volume storage, the lo-side boxes keep frequently used tools at arm's reach from the side, and the rear of the bed stays open for materials. Confirm compatibility with your truck's bed length before ordering both.

Are aluminum or steel lo-side boxes better?

Aluminum side mount boxes (UWS) are lighter and naturally rust-resistant — ideal for wet climates or frequent reinstallation. Steel boxes (Weather Guard, Brute) are heavier but typically lower cost with powder coat corrosion protection. Choose aluminum for weight savings, steel for maximum security and value.

What size side mount tool box do I need?

Most full-size trucks fit lo-side boxes in the 48"–72" range. Crew cab trucks with 5.5 ft beds typically fit a shorter box around 36"–48". Measure your usable rail space from cab to tailgate, accounting for the wheel well, before ordering — or use the vehicle filter on this page to find confirmed-fit options for your specific truck.