tonneau#Origin

Image:1910 Buick Tonneau rear.jpg side-entrance tonneau without tonneau cover]]

File:Sunbeam 1903 at Regent Street Motor Show 2011.jpg rear-entrance tonneau]]

A tonneau was originally an open rear passenger compartment, rounded like a barrel,Oxford English Dictionary, Oxford University, 2011 on an automobile and, by extension, a body style incorporating such a compartment. The word is French, meaning 'cask' or barrel, cf. “tun”.{{Cite web|url=https://en.wiktionary.org/wiki/tonneau|title = Tonneau|date = 25 July 2021}}

Early tonneaus normally had a rear-facing hinged door, but single and dual side doors were soon{{when|date=November 2019}} introduced.

When the street was muddy or dirty, the car could be backed up to the curb so tonneau passengers could exit directly onto the sidewalk.

Historically, tonneau cover referred to a flexible temporary cover (typically made out of leather or canvas) for an open area of a vehicle.

In current automotive terminology it typically refers to a hard or soft cover that spans the back of a pickup truck to protect the load from weather elements or thieves, or to improve aerodynamics. Tonneau covers come in many styles that fold, retract, or tilt open, and can be locked shut. Common materials used include steel, aluminium, canvas, PVC, fibreglass, and carbon fibre.

Tonneau covers are also used to cover and protect open areas of boats. Many of these covers are made of waterproofed canvas and are held in place by snaps.

The older, original tonneau covers were used to protect unoccupied passenger seats in convertibles and roadsters, and the cargo bed of a pickup truck or coupé utility.

Modern hard tonneau covers open by a hinging or folding mechanism, while segmented or soft covers open by rolling up or folding. Hard folding covers are more popular with truck owners because they offer better protection, security, and waterproofing.{{cite web |url=https://f150lab.com/best-hard-folding-tonneau-covers-for-ford-f150/ |title=Hard Folding Tonneau Covers for Pickup Trucks |date=August 21, 2021 |website=F150Lab |access-date=April 4, 2023}}

Truck and car tonneau covers keep items out of the weather and out of sight of potential thieves.{{Cite web | title = Toyota Glossary | url = http://www.toyota.com/help/glossary.html | access-date = 2011-01-24 | url-status = dead | archive-url = https://web.archive.org/web/20110415163840/http://www.toyota.com/help/glossary.html | archive-date = 2011-04-15 }}

The year and model of a truck determine the size of its tonneau. Many dealers will recommend using a tape measure to measure the truck bed.{{Cite web |last= |date= 10 April 2024|title=How to Measure for a Tonneau Cover? |url=https://mostplusauto.com/blogs/articles/how-to-measure-for-a-tonneau-cover |access-date=2024-04-30 |website=MOSTPLUS |language=en}}

Early open-bodied touring-type automobiles used tonneau covers to protect unoccupied rear seats. As early as the 1930s, lakes racers, searching for an extra competitive edge, imitated early automobile construction and skinned the cockpits of their roadsters and streamliners with removable canvas. The skins covered gaping cockpits that would otherwise disturb airflow and create undue drag; as a result, tonneau-equipped cars ultimately went faster with a given amount of power.{{Cite web| title = Street Rodder, March 2007 | work = Street Rodder | url = http://www.streetrodderweb.com/tech/0703sr_tonneau_cover_installation/index.html | access-date = 2011-01-24}}

File:MGA DSC 4480.JPG]]

Tonneau covers are used in lieu of hard or soft convertible tops on open sports cars such as the MG, Triumph, Austin-Healey, and Porsche Boxster.{{Cite web | title = Installation of Tonneau Cover | url = http://pages.sbcglobal.net/brackenrig/pORSCHEEEEGp6NUM897.pdf | access-date = 2011-03-09 }}{{Dead link|date=July 2018 |bot=InternetArchiveBot |fix-attempted=no }} These covers, often made of natural or artificial leather, cover the entire passenger compartment, and are zippered so the driver's seat can be uncovered while the rest of the interior remains covered.{{Cite web| title = Porsche wind & weather| url = http://www.porsche.com/usa/accessoriesandservices/personalisation/tequipment/boxster-986/windandweather/n293 | access-date = 2011-01-28}}{{Cite web| title = MGA tonneau cover| url = http://www.mgaguru.com/mgtech/top/top100.htm | access-date = 2011-01-28}}

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File:1934 Ford Coupe Utility.jpg was a 1934 Ford Coupe Utility. It included a tonneau.]]

Tonneau covers{{Cite web|date=2021-07-31|title=Different Types of Tonneau Covers » Truck Observer|url=https://truckobserver.com/different-types-of-tonneau-covers/|access-date=2021-08-01|language=en-US}} are used in coupé utility cars and pickup trucks to cover and secure the cargo bed and come in a variety of styles. Mainly they are categorized by material Soft or Hard covers. Soft covers can be rollup or folding and Hard covers are rollup, folding or one piece.

The most common style is the roll-up tonneau made from cloth or vinyl,{{cn|date=February 2024}} which uses a rib-like structure to support the fabric and keep it taut and roll up toward the cab of the truck. A snap-based system is also used, but has become less common due to truck owners not wanting to install the snaps on their vehicle as they typically require drilling or permanent adhesive.{{Cite web|url=https://autoemc.net/blog/types-of-truck-bed-covers/|title= Types of Truck Bed Covers|publisher=Auto |date= August 31, 2022}} Hard roll-up tonneau covers are more firm than regular roll-up tonneau covers.{{Cite web|url=https://autoemc.net/blog/do-tonneau-covers-save-gas/|title= Do tonneau covers save gas|publisher=Auto |date= August 31, 2022}} They are made of a wall of individual aluminum slats, covered with soft vinyl. In the unrolled position, these aluminium slats form a hard aluminium shell, which not only covers the cargo inside the bed, but also may support loads up 400 pounds on top of it.

Another style of truck bed tonneau cover is a retractable unit, which is mounted at the front and sides of the bed and rolls up or retracts from the tailgate towards the cab. The retractable tonneau is typically made of vinyl, plastic or aluminium. Retractable tonneaus are more secure than soft tonneau covers, since they usually lock and are made from a harder composition, but they take more time to install and are designed for semi-permanent installation.{{Cite web|url=https://autoemc.net/blog/how-to-install-a-tonneau-cover/|title= How to install A Tonneau Cover|publisher=Auto |date= August 31, 2022}}{{Cite web|url=https://bedcoversfortrucks.com/|title= Bed Cover For Trucks |publisher=Auto|date= July 15, 2022}} There are two popular categories of tonneau covers by Retrax: manual and power. A manual tonneau cover must be moved by hand, while a power tonneau cover is moved by its own motor.{{Cite web|url=https://retrax.us.com/|title= RETRAX Retractable Truck Bed Tonneau Covers Official Website|publisher=Auto |date= February 13, 2025}} Fiberglass, hard plastic, or aluminium tonneau covers are also common. Some may be painted to match the truck, are solid in construction, and can be locked. These covers are usually heavy and require gas struts to assist in opening and closing. They operate much like a vehicle's hood, typically opening from the tailgate end of the bed (back to front). Some have multiple compartments that open front to back, back to front, side to side, or even rise vertically. Fiberglass, hard plastic, or aluminium tonneau covers are sometimes installed as a factory option on new vehicles.{{Cite web|url=https://autoemc.net/blog/a-r-e-fusion-tonneau-cover/|title= Are Fusion Tonneau Cover|publisher=Auto |date= August 31, 2022}}

Many sellers claim that tonneau covers improve gas mileage because they make the truck more streamlined. However, air currents create a wake inside the pickup bed, which helps the aerodynamics.{{Cite web|url=https://autoemc.net/blog/what-is-a-tonneau-cover/|title= What Is A Tonneau Cover?|publisher=Auto |date= August 31, 2022}} A tonneau cover interferes with this wake, and scientific tests have shown little to no improvement in mileage by using a tonneau cover traveling at less than {{convert|70|mph|abbr=on}}. A similar effect is seen when the tailgate is down and the mileage goes down.Improving Aerodynamic Characteristics of A Dodge Ram Pickup Truck, 1997, Todd J. Ortolani, Vanwijak (Kehm) Ewosakul, Western New England College.[http://kwc.org/mythbusters/2006/10/episode_64_more_myths_revisite.html Annotated Mythbusters] Mythbusters Episode 64{{Cite web |url=https://f150lab.com/do-tonneau-covers-save-gas/ |title=Do Tonneau Covers Save Gas? Mythbusters Findings |publisher=F150Lab |date=August 27, 2021 |access-date=April 4, 2023}}

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Tonneau case is used to describe a type of watch case, with rounded, bulging sides resembling a barrel (or cask).

File:Tonneau Wristwatch.jpg

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Category:Automotive body parts