How to DIY Shelves in CM Truck Bed Tool Box | A Straightforward Guide

If you want shelves inside your CM truck bed toolbox, the path forward isn’t a universal bolt-in kit. CM doesn’t publish a DIY shelf-installation how-to for owners. The company’s official position is more specific: shelving is an upfit option available through your nearest distributor, and it applies to the SK Deluxe Steel Utility Body model line. For everyone else, a careful custom approach works—provided you protect the box’s weather seals and mounting integrity.

What CM Officially Offers for Toolbox Shelving

Here’s the key fact to know before you buy anything: CM’s toolbox shelving page ties shelving to a specific body style. The SK Deluxe Steel Utility Body’s front utility boxes can be customized with CTech, Stellar, or adjustable shelving during the upfit process, and that work goes through your nearest distributor. This isn’t a DIY kit a homeowner can buy.

Your other CM models weren’t left out of the quality focus, though. The TM Deluxe Steel Tradesmen Body features MegaBox toolboxes that are 54 inches wide with easy-access suicide doors (available only on the 11’4″ TM models). The SK Steel Skirted Body includes adjustable, lockable chrome T-Handle compression latches and automotive-style weatherstripping on all toolboxes.

Can You Build Shelves Yourself Without the Upfit?

Yes, you can build custom shelves for your CM toolbox, but you’ll be working with one hard constraint: the weather seal.

When you add shelving, you are not drilling new holes in the lid or walls if you can avoid it. The most reliable approach uses a shelf board that sits on the existing bottom of the box, sized to fit snugly between the front and back walls. To keep it from sliding, you can either use a small, strategically placed bracket glued with strong automotive adhesive, or a friction-fit foam strip along the bottom edge. Avoid screw anchors that penetrate the box walls—those create future leak points and void the integrity CM builds into the weatherstripping.

If you have a TM model, the 54-inch width gives you generous length for a full-width shelf. For the SK body, measure the interior width first, then subtract a half-inch so the board doesn’t bind against the walls. Cut your shelf from 1/2-inch or 3/4-inch plywood, and seal the edges with a moisture-resistant wood sealer that lasts under the lid’s compression.

Securing Your CM Toolbox After Shelving Work

Whatever you do inside the box, the box itself must stay firmly mounted. CM’s manual confirms its toolboxes use slam latches or compression T-handle latches, so the box hardware is solid. For the mounting itself, Home Depot’s guide for installing a truck tool box is the reliable general procedure: add padding between the box and the bed rail, position the box, drill as needed, then secure it with J-hooks and nuts or bolts, depending on your truck and box design. Ensure the lid clears the truck cab and the hinges move freely before you tighten everything down.

If you’re using support legs, a Northern Tool manual adds specifics: secure the support legs to the box and the truck bed, drill 1/4-inch holes into the truck body for the legs, and attach the legs directly to the truck floor—never on top of a bed liner or floor mat.

What to Check Before You Mount Shelves

Before you commit to a design, run through the points that decide whether your shelf lasts a season or a decade:

• Verify your model’s upfit eligibility. The only CM page that explicitly mentions shelving ties it to the SK Deluxe Steel Utility Body through a distributor. If you own a different body, CM’s published pages don’t confirm a factory shelf option for it, so plan a custom build.
• Protect the weatherstripping. Check the D bulb seal every three months. A cracked seal lets in moisture and ruins tools, regardless of how good the shelf looks.
• Choose non-invasive mounting inside the box. Prefer friction-fit boards or adhesive brackets over screws that penetrate the walls. Your box’s weather sealing matters more than a perfectly level shelf.
• Re-check the box mounting before you load it. After you finish the shelf work, verify the J-hooks, support legs, and nuts are tight, and that the lid still closes with compression. A box that shifts on the road will undo your shelf work fast.

If you’re weighing a new rig or upgrading your current setup, our tested roundup of the best tool box trucks can help you find a model with the factory storage you actually want.