Truck Tool Box Configurations by Trade: Topside vs. Underbody

The best truck tool box configuration puts the tools you reach for most where you can get them from the ground, and keeps as much open deck as your work needs. On a flatbed or stake bed, that usually means topside boxes, underbody boxes, or a mix of both. The right mix depends on your trade: what you carry, what has to lock up, and how much deck you need for materials.

Below we compare the two box types, list real sizes from past Alumbody builds, and suggest starting-point layouts for six trades. Treat the layouts as suggestions. The right one is the one that matches how you work.

Topside vs. underbody tool boxes

A topside tool box (also called a topsider) sits on the deck along the side of the bed. An underbody tool box mounts beneath the deck, in the space between the deck edge and the truck's frame. Here's how they compare:

When topside boxes make sense

Choose topside boxes when you work standing at the side of the truck and reach for the same tools many times a day. A long 72" or 88" box keeps hand tools, fasteners and meters along the side of the deck, where you can reach them from the ground. The trade-off is deck width: two topside boxes narrow the open area between them, so check that your widest regular load still fits.

When underbody boxes make sense

Choose underbody boxes when you need the whole deck for pallets, sheet goods, equipment or debris. They keep tools stowed below the deck and leave the top completely flat. Their size depends on what's under your truck, so they're sized to clear the wheels, fuel tank and exhaust on your chassis.

Using both

Plenty of work trucks run both: topside boxes for daily hand tools and underbody boxes for heavier gear. Real Alumbody builds with that combination include a GMC Sierra 1500 6'6"×9' flatbed with two 16"×13"×88" topside boxes and two 14"×12"×30" underbody boxes, and a Toyota Tundra 6'6"×7' bed with two 16"×13"×72" topside boxes and two 14"×12"×30" underbody boxes.

What about crossbed tool boxes?

A crossbed box spans the width of a pickup bed just behind the cab, resting on the bed rails. It's a familiar setup on a factory pickup bed. On a flatbed, a box across the front takes up deck length instead, so it's worth weighing against topside and underbody boxes, which leave the full length of the deck open.

How to choose your tool box configuration

• What do you reach for at every stop? That belongs in a topside box or the most accessible underbody box.
• What has to stay on the truck overnight? Tools and meters left on the truck belong in a locking box, not on a rack.
• How much open deck do you need? Pallets, sheet goods and debris call for underbody boxes and a clear deck.
• What's long? Ladders, pipe and lumber ride on a ladder rack or a pipe/lumber rack, not in a box.
• Which gates? 22" fold-down gates make side loading easy; 30", 38" and 41" lift-out gates give taller sides. See gate options.
• Will you add a liftgate? Plan the rear of the bed around it. See liftgates.

Starting-point tool box layouts by trade

These are suggestions, not rules. Where we can, we point to a real Alumbody build with a similar layout.

General contractor

Two topside boxes for hand tools and fasteners, either 16"×13"×72" boxes or 21"×13"×72" contractor boxes, with a ladder rack overhead. Add underbody boxes if you want a spot for cords and heavier tools. Similar real builds: a Chevy Colorado 6'×6'6" flatbed with two 21"×13"×72" contractor boxes and a ladder rack, and a Colorado 6'×7' flatbed with two 16"×13"×72" topside boxes, two 14"×12"×24" underbody boxes, a ladder rack and a dock bumper.

Plumber

Topside boxes for hand tools and fittings, underbody boxes for heavier tools, and a pipe rack for long stock. A vise mount area on the deck helps if you cut and thread on site. Similar real build: a Toyota Tundra 6'6"×7' flatbed with two topside boxes, two custom underbody boxes, a vise mount area and a removable PVC pipe rack.

Electrician

Two long topside boxes, 16"×13"×72" or 16"×13"×88" on a longer deck, for meters, hand tools, connectors and fittings. A ladder rack carries extension and step ladders, and a pipe rack handles conduit. Underbody boxes hold cords and heavier tools.

HVAC

A taller topside box for bulkier gear, such as a 24"×24"×36", plus underbody boxes such as 14"×12"×30" for parts and tools, leaving deck space for equipment. If you move condensers or other heavy units, a liftgate and well-placed tie-downs make sense. Similar real build: a Chevy Silverado 2500 6'6"×9' flatbed with topside boxes including a 24"×24"×36", two 14"×12"×30" underbody boxes and a dock bumper.

Landscaper

Keep the deck open for mowers, plants and debris, and put storage underneath: a large underbody box such as 18"×18"×48" holds hand tools and smaller equipment. An aluminum stake bed with 38" or 41" lift-out gates contains loose loads, and a rake and broom rack keeps long-handled tools off the deck. Similar real builds: a Ford F-550 8'×12' flatbed with an 18"×18"×48" underbody box and a dock bumper, and a Ford F-150 with a rake and broom rack between the headboard and the cab.

Mobile mechanic

Two topside boxes such as 18"×18"×60" for hand tools and sockets, underbody boxes for heavier items like jack stands, plus D-ring tie-downs, a hitch, LED work lights and a reverse camera. Similar real build: a Ford F-150 6'6"×7' flatbed with two 18"×18"×60" topside boxes and 18" fold-down gates.

Hardware and planning

Our tool boxes are aluminum, like the bed. For wet or cold climates, stainless steel installation hardware is available, so ask about it if your truck sees road salt or a lot of rain.

If you can, plan the boxes when the bed is designed. That way the box sizes, gate layout, liftgate and chassis clearances are worked out together instead of fitting boxes around what's already there. Browse real builds on our tool box page, read how this compares with a compartment truck body in service body vs. flatbed with tool boxes, or send your truck and trade through the quote form for a firm quote within 2 business days.