The UnderCover Swing Case is in a class of its own. A smaller tool box, the swing case mounts to the side of the truck bed and fits behind the wheel well, making use of otherwise unused space. It swings out 180 degrees for easy access and can hold up to 75 pounds. It's lockable, too, so you know it's secure even if your tonneau cover is left open.

Access makes the Truck Bed Accessory Smart Pack, which includes three very useful products: a 12-inch LED truck bed light, a tailgate seal, and the EZ Retriever II, which is a grab handle that extends up to 8 feet in order to reach and retrieve items in the truck bed. The EZ Retriever II can also be used as a cargo bar to keep items confined to one section of the truck bed so they don't shift and cause damage. The Access EZ Retriever II is also available for separate purchase. The tailgate seal can be cut to length and installs easily with its adhesive backing. The LED truck bed light can also be placed with included adhesive backing, it just needs a power source in the truck bed.

Truck bed lights, like those made by Recon, are a simple product that make life so much easier. They mount to the side of the truck bed with automotive grade adhesive, making it easier to see in low light conditions. Truck bed lights can also be used in other applications, including in RVs, boats, and more.

Full bed liners like the BedRug] work well with nearly every tonneau cover on the market. Made to protect the truck bed from damage, full liners extend up the sides of the truck bed to offer complete protection. There is little to no interference between the top sides of the liner and the bed rail where the tonneau cover installation clamps are located. Should the liner interfere, it can be trimmed for a better fit. Bed and tailgate mats do not interfere with a tonneau cover.

Most tonneau covers become more secure than the cab when paired with a locking tailgate, so the Pop & Lock is the perfect accessory for tailgates that don't have an existing lock. It comes with two keys and mounting hardware, which can be installed in minutes with basic tools. It works with backup cameras and helps prevent tailgate theft, too.

Bed caps attach to the top of your truck's bed rails, creating a barrier between damaging cargo or falling hazards and your bed's sheet metal. They work in conjunction with tonneau covers to prevent moisture from entering your bed.

Bed rails mount to stake hole pockets located in the top of the bed sides and have little to no interference with low-profile tonneau covers, though they won't work in conjunction with high-profile covers like soft tri-folds and certain roll-ups. These bed rails are multi-purpose and can serve to secure cargo or can be used as a grab handle when climbing into the truck bed. They do not interfere with the underside of the bed rail where the tonneau cover mounts.

A bed extender gives extra you room in your truck bed by making the lowered tailgate a temporary part of the bed. With the tailgate lowered, the extender mounts to the inside of the tailgate below the deck rails and provides a barrier so large cargo cannot slide out.

Bed extenders, like this one from AMP Research, can be used with most tonneau covers, including hard and soft roll-ups, hard and soft folding covers, and retractables. Hinged covers may not be compatible with bed extenders as they may not be able to fully latch closed. Whether the tonneau cover is secured open or closed, it will need to be securely latched in place, whether at the bulkhead with straps, buckles, or prop rods, or clicked into place at the tailgate when the extender is deployed.

Tool boxes are synonymous with work trucks, and there's a wide range of tool boxes that are made to fit with the tonneau cover of your choice, including hard and soft folding, soft roll-ups, retractable, and hinged covers. The Extang Solid Fold 2.0 toolbox tonneau cover is made to fit behind most 18 to 20-inch toolboxes, which are sold separately from this cover. If you've already got a standard-profile toolbox of this size and want a tonneau cover to go with it, this is a great option. Another option that comes with a tool box, Truck Covers USA makes the American Work Cover Jr., a retractable cover and toolbox combo that are specifically made to work together; the toolbox's low profile doesn't reduce rear visibility nor does it take up additional space in the bed as it sits on top of the canister.

Some tool boxes are also made to fit under a full length tonneau cover, including BAK's BAKBox 2 and TruXedo's TonneauMate tool box. The TonneauMate can be installed without a cover and has a keyed lock for extra security. It also sits about 6 inches off the cab, so it doesn't take away from the length of the truck bed. Though sold separately from tonneau covers, the BAKBox 2 does require a BAKFlip tonneau cover for installation as it mounts to the cover's rails. The tonneau cover also serves as a lid for the box. Similar to the TonneauMate, the BAKBox 2 does not extend to the truck bed floor. BAK also notes that its insulation makes it a great ice chest for tailgating and outdoor adventures.

Most truck bed tie downs, like the pictured Bull Ring retractable tie down, mount into the stake hole pockets on top of the bed rails. If your tonneau cover's rails don't overlap the stake hole pockets, there should be no interference. Clamp-on tie downs and cargo cleats, however, will only work with some tonneau covers as they mount to the side of the rail where the tonneau cover mounts.

Cargo sliders, like the Decked System, will likely not interfere with a tonneau cover as the installation hardware is primarily located in the bottom half of the truck bed and does not make contact with the bed rails.

Cargo bars stretch from one side of a truck bed to the other and keep cargo from shifting inside the truck bed. Cargo bags, like the Load Handler CargoCatch, have much the same purpose, though items are contained within a bag. Whether holding a bag or not, cargo bars like the Core Big Maxx HD are adjustable and secured into place with tension via ratchet or with an inner spring. No wider than pipe tubing, these bars can be placed at any height along the inside of the truck bed and therefore do not interfere with tonneau covers. A cargo gate, however, could interfere with a tonneau cover if it makes contact with the side rails when installed.

The Du-Ha Humpstor provides extra storage space in the truck bed, above the wheel well but under tonneau covers. Its heavy-duty construction and length allows space for longer, heavier tools. It's even long enough to accommodate a rifle, making it perfect for hunting season. Installation is easy, too, with brackets that clamp to the bed rail.

Headache racks are one of the best multi-purpose accessories we carry. Not only do they protect your rear window from debris you may be hauling, scratches from tool box lids, and more, but they also offer vertical storage for smaller cargo and tools as well as an additional anchor point for larger items. The Backrack Original headache rack is a top seller due to its low profile-design that doesn't decrease visibility or interfere with parking.

Truck racks mainly mount to the bed rail through stake hole pockets. While some truck racks are heavy-duty and are not compatible with tonneau covers, others are made to work with specific tonneau brands.

• TracRac Truck Racks (SR, TracONE, and T-Rac) fit the GatorTrax and Retrax retractable covers
• Pace Edwards Contractor Rig fits covers that use Explorer Rails (BedLocker, JackRabbit)
• Access Adarac Aluminum Pro Series fits LOMAX, LOMAX Professional Series
• ProRac STR Soft Tonneau Cover Rack fits Extang Classic and Black Max, TruXedo TruXport
• Truck Covers USA American Truck Racks fits Truck Covers USA tonneau covers